The average humidity in the enclosure should be about 50%. The snake's water bowl should be large enough to fit his entire body inside to soak, so he can regulate his own level of moisture. You can also add a "hide box" with damp moss. This can be as simple as a plastic container with a hole in one side, which will retain a higher amount of humidity than the rest of the enclosure and allow your snake to visit it as he wishes -- still, the box doesn't need to be any higher than 65% humidity. Conditions that are too damp are also a health problem for ball pythons, so as long as you're providing a large water dish and your snake is shedding well, your setup is probably fine. Enjoy your BP, they're great snakes!