My T's schedule is full but he gives 55 minutes. I don't feel bad going till 5 minutes before the hour because he often starts 5 min late, offering me a glass of water then going to get one for himself. If he did go over time, I'm sure he wouldn't charge me. Once I was out of town visiting family who were sending into a tailspin of anxiety and I emailed him and he offered a phone call. We talked for a full hour. When I got back and tried to settle with him, he said there was no charge, that it was built into the fee. I said no, and insisted on paying because I don't want special favors.
Anyway, I would definitely address this issue with your T. It's really not ethical, in my opinion, especially if he is in charge of time-keeping.