implementation shortfall complications?

sorry, don’t have time to look this up in a detailed way for myself. i understand there’s been some confusion on the benchmark price (close??) seems like all examples are you putting in order at $24.90, but it closes as $25.00 unfilled first day, and we use $25 as benchmark… but what if it you get filled the second after you put in the order? then surely the closing price isn’t the benchmark. maybe i misunderstand too. and then someone told me that the absolute final price is the closing price after you cancel not the price when you cancel? any thoughts? this is more complicating stuff, and i will probably look at it in CFAI stuff. thanks in advance!!!

I’m ignoring everything on this except the following: I believe the original credit goes to bchad for posting.