Negative Feedback for no given reason

[cs6424]

I'm just looking for clarification on some negative feedback I got for seemingly no reason. The only thing they wrote was "Fast shipping!" which seems like a complement rather than a complaint. To my knowledge, the label and item description were correct. I'm only selling to de-clutter, and this is my first time getting negative feedback after about 20 sales. What, if anything, can do about this unclear negative feedback?

Some details in case they might help: The item sold was a vintage magazine. Used. And the price paid was lower than what I was asking for because I also had the "best offer" option on. I paid the shipping as well.

[bearswatching]

My theory? There are still buyers  who are sadly years behind the times and still think sellers can leave them retaliation feedback if they leave a negative. Ran into one recently. When I told her that hasn’t been allowed for 14 years and it was a huge announcement she said she never reads announcements because they are mostly useless. Then asked me for a QUICK synopsis of what the highlights were since 2008. Sure, wait for it😁

[soh.maryl]

If you are searching for clarification on that confusing feedback, wouldn't you want to contact the person who left it, in this case your buyer?  

[cs6424]

Update: Following the advice of several responders, I asked eBay to remove the negative feedback. It took them a lot longer to get back to me than they said they would, but it was removed because it was against the rules.

Thank you to everyone for the help!