Our general rule is that you add another box when the colony is covering 60-80 percent of the frames in a box. (Kirk says 80-90 in the video but don’t let them get that crowded if you can avoid it). This is a new package started 21 days ago in drawn comb from a deadout. This means that the capped brood will be hatching in the next couple of days and we will start seeing exponential growth in our colony. They are out of room and need a new box, but knowing that the new brood and exponential growth is starting in the next couple of days means that if they were just 60 percent we would add another box as well because they would run out of room with the new bees before we get back for our next 2 week hive check.