it sounds familiar but the big time gap is odd. i work at a high volume store- highest grossing in my district and we strictly stay until 9:30 (after closing @ 9). My SM explained it to me this way: Hours are earned, and if you leave early just because you finish early some nights, it will be seen as you don’t need that time and they will cut hours. but 8-10 is a huge gap i don’t see why they would do that.

Every store I've worked at you could leave when you were done with all your closing tasks.