The best way to work with a thermostat/UTH combo is this: Make sure the stat probe is taped to the UTH over the center. Then, adjust the setting on your thermostat until you get the desired 93-95 reading on your thermometer INside the enclosure right over the UTH spot. You want the place inside the cage right over the heat source to be the hottest acceptable temperature, then the temp on top of the bedding will be a few degrees cooler.

The numbers on the thermostat are NOT what you would be concerned about. The number you want to watch is that of the thermometer inside. I have several stats set to over 102 in order to get the 94 I want inside.

Also, tempguns are usually the most accurate things out there, but they can be a little tricky to use when they're the smaller type. Why do you ask about testing? What is the difference between your digital thermometer reading and your temp gun reading?