Absolutely; however, would it have been fair to let you leave at 9 hours and someone else at 15?
The way I read it was he was trying to make sure that everyone was able to leave at about the same time.
A few years ago our center manager st the time pulled the same stunt. I was done at 1830 but was forced to stay and run off a residential split. I punched out at 2130. I was

but I knew that he was trying to be fair to everyone.