Explain shipping metric for me? Can one package be counted for each item sold?

[montana_echoes]

So it appears that my shipping metric, which currently 3.41% late shipments, is actually counted per item NOT as per order. So if one buyer asks me to delay the shipment by a few days, and he bought 20 items... then I get hit 20 TIMES for late shipping for all those items. Not for ONE order... for EACH item.

So If I ship 20 packages out on time and even early and then that one package for 20 items is requested to be mailed late, I sell 40 items, get hit with 20 late shipping hits due to ONE package.

I'm trying to figure out how this is fair? The above isn't exactly the number of packages/ items as what happened, but I've simplified it for clarification.  

So, is the metric counted per order, or per item?? I had one person purchase 120 items last month... and I rolled those 1200 feathers into one listing to make it easy on him.... guess I should have let him buy it as 120 items as that would have UPPED my shipping metric when I mailed it the day after the order -- right? 

Don't confuse this with Top Rated seller designations, I don't fool with that, (not worth shipping in one day to gain 1% reduction of a 9% fee)  but I have absolutely seen a crash in sales every time my shipping metric for late shipments falls above 3%. Every time! So I'm being punished with less sales just because I was dumb enough to combine a persons items into one listing,  or I was silly enough to agree to late ship for a buyer who wanted me to wait. 

I had truely thought the Shipping metric was number of late Packages a seller shipped out. But I've got 38 late shipments for the last year -- and I didn't ship out 38 packages late. So I started digging into which items, and sure enough, there's a 4 item order, sent a day late, its counted 4 times! A 10 item order that I'm sure he requested it be delayed, its counted as 10 lates! Talk about stacking the deck, ebay, and man oh man, that 1200 feather order I should have let him buy it as 120 packages (10 fthrs per pack) so that would have wiped out the shipping metric problems and, I'd be back to having excellent sales again and not hidden in search. I guess I'm the stupid one for making it easy on a buyer.