What is correct humidity Level for tank

I am on a couple of facebook groups.
One says cool side humidity should be 30%-40% during the day.
The other keeps telling me it has to be below 30% on the cool side.

I live in Dallas texas. It can get humid here. right now, the room he is in has 35% humidity.
I could throw a dehumidifier in the room, but I am not sure they even work past 35%-30%.

I have two eva-dry wireless dehumidifiers in his tank along with an exhaust fan for air flow. he is in a 40g tank.
I have the humidity at 31%-33% (its higher in the middle for some reason).
I am using hygrometers. I have three in there. One on the back wall on the hot side, and back wall of the cool side. And one in the middle of the cool side.
Substrate is 85% tile with the last portion reptile carpet.

Is this good, or do I need to lower it? This is cool side. his hot side will range from 15%-25% depending on how I adjust the temps.

Anyway, just want to know what the proper humidity should be during the day, on cool side...the range?

You only need one hygrometer---placed on back center of wall - its going to tell you basically the over all tank besides the basking area where it will be lower because of the heat --- your tank is fine at 40-50% right now my tank is at 26% but its winter in MN -- dry -- in the summer they run higher around 40 -50 --- you dont want your tank over 70% --- anything below is good --- and you dont want it lower than 20 -25% --
Karrie