I’ll second the statement that it isn’t unusual to set the temperature higher than it reads inside at the glass. Even with my rhp’s, each cage is custom set to reach the surface temperatures I want below the unit. Of my 4 uth, 3 are set slightly higher than the inside temp. The 4th is a mini I purchased yesterday for Selene’s quarantine tub because the one I ordered was delayed and won’t arrive until next week. It is HOT and I had to set it for low to mid 80’s for my tub surface to be 90F. Temp guns are invaluable. I’ll be glad when my Ultratherm gets here.