| Ok firstly, the night dial isnt designed to be your not temp, it is the dial that drops the standard dial by in temp.
ie normal dial set at 30 and night dial set at 5, then it drops the standard dial to 25.
Other than that, yeah i have found the majority of thermostats are never accurate to what the dials say. So it is always best to set your thermostat off your thermometer. This is the best and most accurate way.
hope that helps
Cheers | 
