Your heater should be set to the temp you want the shed to be. I use an oil filled radiator in my shed. It's set to 85. The majority of the shed will read anywhere from 80 to 90, good temps for my leopards. At night when basking lights are off it will read 77 to 83. Move the mat away from heater and set to 80 if that's what you want it too be. If it's not too close to the heater, it likley will work properly.