What type of bator do you have? Some are usually duds, cooking them depends on the bator you have, and drafts in the room. If you have to many chicks in the brooder, you can always make it bigger! Try not to sweat it, its is such a fun experience!
Sorry...terrified of hatching......you all made it sound fun....but I'm convinced I'm going to a. have a bator full of duds. b. cook all the babies or c. have WAY too many chicks in my brooder