The thermostat probe will regulate the temperature of the flexwatt itself, and then floor temperature where the flexwatt is positioned will either be approximately the same temperature or slightly lower. Use the thermostat to pick your desired temperature and then use a temperature gun to measure the temperature on the inside floor of the cage. You can then adjust the thermostat to compensate for whatever drop there may be. People programming their thermostat to be slightly higher than their desired temperature is not uncommon.