I have 2 identical thermostats in my 20 gallon for the 2 UTH's. The hot side stays set at around 94 degrees and keeps the surface at 89-90. The cool side is set at 80 and it keeps the surface at 80. So I trust my temp gun not the thermostat readings. One way to test the temp gun is to aim it at the wall right next to your home thermostat. Those are typically pretty accurate. Some people fill a glass with cold water and a good amount of ice and it should read close to 32 degrees. When we brought our first BP home he would move around in the beginning from hide to hide. The last few months he has spent 90% of the time in the cools side. Are both of the hides in your tank identical? It is important to make sure the BP is choosing the cool side because of the temp and not because it doesn't like the hide on one side over the other hide.