I'm not clear on how your "booking" question relates to a cancellation term. You don't get a refund for booking, you get one for cancelling, if you've made a deposit.

If you book a room 100 hours out, with these terms, and cancel within 28 hours, you pay nothing. If you cancel after 28 hours later (within 72 hours of checking), you are charged the cancellation penalty.

You can book any time you want to. If it's past the cancellation deadline, you typically get a notice that any change/cancellation after clicking "OK" is subject to a penalty.