You asked for it... this will be a long one lol.
I can see them. As per usual, Ebay offers no real explanation, the bubble pop ups don't explain really anything and no one was paid with the millions of dollars they make per day to leave us anything helpful to figure it out lol.
I have studied internet marketing and SEO for almost 2 decades, with a core in ebay sales specifically, and they are using terminology that I'm familiar with but in ways that just make no sense, are incomplete or seem embellished seemingly all the time.
I'll explain what I can, though in my personal opinion, many of eBays shown metrics are embellished, specifically "impressions".
An impression is not a view or click, just a time that a link to your listing was there on screen for a viewer to see. This will include when a link to a listing is there in the search result that a viewer has in front of them even when they have not scrolled far enough to see it.
1. "top 20 search slot impressions":
This would be how many times your listing is displayed for a human viewer to see in search results in the first 20 placements of those results. This one specifically I'm nearly certain is embellished. I actually found this thread looking for what they could possibly mean by "top 20 search results". While it is obvious they mean exactly what I thought they did, I have several listings that never show in those 20 and are consistently showing on 2nd page that they say I've gained upwards of 400% positive change in this metric. Meanwhile, the only keywords that these actually do show up in that category for (in the top 20) are very long tail and have been showing up right where they are today since the day I created the listings. These keywords are also basically never searched for here on eBay leaving essentially no way they could've increased by this much lol.
Now, assuming this metric was correct you would watch this to see if your listings are performing better in search results. Attempt to get more of your listings to show in the first 20 and so on. It gives no indication of how to make them perform better though. This you have to know. Mostly you would want to work on your SEO.
2. "rest of search slot impressions":
This is any other time that links to your listings appear to a real human in search results. This would include any listing appearing from the 21st position down, even ones on later pages, as long as a real human actually clicked to that page of results and the listing showed in that page of results for them to see (even if they did not scroll far enough to actually see it on screen). Again, assuming non embellished results, these would be listings you might want to work on your SEO for each of the listings in this metric.
3. "non search impressions":
This is any time your listing is shown on screen that was not in a search result here on eBay. This could be from links on your page that you have placed manually or from those "other buyers also looked at" things at the bottom of listings and that sort of thing. Literally any time that your link is there on screen (even if not scrolled to) for a human to see that is not in a search results page. Often this will be much higher than the other metrics. It's similar to cross promotion impressions like if you had a link to your product on someone else's page or something else that is at all similar.
Looking at these 3 metrics, for you to use them to your benefit, I would strongly suggest learning some basic SEO. If you are totally unfamiliar, SEO means Search Engine Optimization. It's just priming your listings to respond better to crawlers so you show up in more organic searches, organic being just from search and no promotions or anything other than raw search.
Your organic impressions show 12.8% and promoted are 87.2%. This means that you are basically only showing in search results because of your promoted listings.
I'm personally right now doing a study on eBay's "promoted listings". My results are not final because I told myself I would give it a month but at this moment I'm about 99% certain that the "promoted impressions" is vastly embellished. Likely from bots and not humans or something, not a lot else it could be. Once my data is in I'll leave a post in one of the threads about promoted listing and are they worth it. Most of the answers over there are from assumptions instead of real data.
As for your question: (Why would I have any impressions for those days?):
I would ask, in what way did you end your listings? Was it vacation mode? If it was then your listings would still be gaining impressions, even views during that time, just not sales. Did you end all of your listings? If you only ended some then you would still see impressions. If you actually ended the listings instead of doing the vacation setting, and ended all of them, then it would go back to what I've been saying about embellished impressions. If your listings are actually ended then they do not exist officially on ebay and therefor will not show in search or otherwise.
4. "Change in top 20 search slot impressions":
The reason you see "-" is because that listing has not changed in regards to showing up in the first 20 listings in search results. When it does change you will see a percentage that is either in green or red with an up or down arrow matching that color to the left of it. Green representing a positive change and red representing a negative change.
5. "change in non search impressions":
Again, you're seeing "-" because there has been no change in the past 30 days to this listing showing up, as a link on screen for a human to see whether scrolled into actual view or not, in ways that are not search results.
As far as whether this is a new roll out I cannot say. These metrics all showed up when I first paid for a store this time. Honestly it is so hard to find things on here, and even harder sometimes to find things again after the first time and there's not much real help for sorting it all out lol. So you could be noticing it simply because you never clicked on that specific link before. I really couldn't say.
