If your thermostat probe is outside of the cage, then you will need to turn it up higher to get the desired in-cage temperatures. Turning the Ranco up to about 100ºF will yield about 90ºF in the cage. This varies a little bit depending on cage type, temperature of room, etc., but try it out. The thermostat probe should be in between the UTH and the underside of the cage, and the thermometer probe should be inside the cage just as you have it.