My broods are usually in the 20 chick range. Sometimes when I open the door they are all out within 15 minutes. A couple of times it has taken the third day before they are all out. Usually if one goes most or all go but each brood is different. Occasionally a few may hang back but they usually like to hang together.
As long as no one is getting hurt I let them work it out at their pace. They always do.