And I tested the tab and it gave me 10 more hours (20 hours total).

No, that is events + reservations, so if I put 10 hours, that gives them 10 reservation AND 10 event hours , essentially 20 hours.
We are hoping for 10 events OR reservations, so if I put 10 hours, they only get 10 hours per month but have the flexibility to use those hours for what they want. 
I was told by some one else that the 2 are separate in the system and there is no way you do that at this point. It also says the same thing on the help menu. That tab just makes it easier for inputting the number niece vs twice.