So I do not know where you are seeing this. Rule of thumb a T5HO fixture single bulb with a 6% or 5.0 UVB bulb at 9 inches down will put out a UVI level of a 3 which is where you want Panthers and Veileds. Higher UVB can cause its own issues as does a lower UVB. IF you have the solarmeter 6.5 then that is fantastic your looking for that 3 UVI level at basking branch.I see a lot of people on recommending 12 % and 10 % repti sun. But I will stick uv meter blow it to see
UVB lighting and supplements work hand in hand so both need to be properly done.