We know the 10 degree variance is in the switch. Putting it right by the light compensates for that issue. It makes the thermostat heat up quicker than the rest of the incubator. That way you are only using the kick on temp an the kick off temp becomes irrelevant. Put it right agents the light an it will cycle to fast to heat the incubator at all. Hundreds of incubators on this board have proven it works. You can hatch eggs using a dimmer switch but you can just easily cook them. This board has proven that many time as well.
