They did this to us as well when we had a guest. It is because they are charging you for two days (the day you come regardless of the time, and the next day). Our guest didn't come in until after 9pm which was even more frustrating. And its $10 per person 5 and up.
Its $10 to stay overnight but have to be out by 11am if you paid $20 you can stay till 8pm. It's only that price for visitors. The same thing happened to me on the 3rd of July but I rolled up it was about 1030 said was going to be saying with my parents overnight they charged me $40 for my boyfriend and I the next day I went to say something at office and they said I was paid till 8pm.
Thanks! Your answer is awaiting moderation.