Ok so I really do not like the bulbs that come with those. They do not give you an exact percentage in comparison to other name brands that do. They also do not give you accurate info based on through screen.
I would replace that one with a 10.0 Reptisun T8 bulb. Distance would be 7-8 inches to the basking brandh below the fixture sitting on the screen. The bulb length you would get is 2 inches shorter then the fixture length. And if there is a plastic piece covering the UVB bulb in the fixture then it should be removed.
@AmandaS I was in petco the other day and the bulb I was talking about up above IS 5.0 it was beside the other brand bulbs and had the same wattage and everything. Also I bought a feeder from full throttle she likes hanging out on top haha.