I believe this is a glitch in the process. I'd give 5:1 odds that it is an error and will be easily corrected. Don't get too stressed until you talk to the hotel.

These fees are intended for folks who reserve 5 nights and then check out in the morning after 4 nights, leaving an unpaid room that would have been much easier to sell with more than 12 hours notice.

You are not in this situation, but I suspect that checking out on the date before planned (before midnight) through someone's logic for a loop.

Let us know.