This is the thermostat I have. I like it because it shows the temperature that I have it set (the bottom number of 75). It also shows the current cage temperature (the top number of 77.9).
Clearly the heat lamp will not be turning on when the indoor temperature is already above 75. But being able to see the current temperature is a good thing.
I also have a 2nd, separate thermometer to read the temp on the other side of the cage. That's the 2nd photo and you can see the cage is slightly cooler on that side.
here with my Mecki-- born 2/12/19