Hi everyone, when we talk about cool side temps does it mean the ambient air temp of a thermometer placed on that side or surface temp of that side?

My BP's are in an acrylic terrarium with a UTH under the terrarium on the hot side (put on a rheostat) and a UTH on the back panel (also on the hot side, so it's a belly/back heat combo) which kicks out the majority of their heat (I will soon be hooking this up to a Helix thermostat). My cool side air temps are about about 79-80, but the temp gun says about a degree lower on the actual ground (I use paper towel). Should I up the UTH that's under the belly to get more heat coming up through the floor or is this okay?

JonV