I am fairly new to this. My girls love showing at the 4-H fair. the first time we hatched eggs we set 12, 11 hatched and grew to be part of the flock we have now. 1 cracked but did not hatch. temp holds very steady, even when you open the top twice a day to turn eggs. humidity can be controlled by tapping off holes here and there on the cooler. 12 eggs is about max for the space.