It looks ok to me. What values are you using?
I've tried with 1, 2, 3 and 4 hours.
In every case I cannot book during ___all the day___.
PS
On the 1.1.3 version I remember past events couldn't be modified.
Now if I set on a Resource 'Minimum Booking Notice = 0' user can do everything even on past reservation.
Don't you think it was better the first version?
I think just the Admin should can modify past events by default.