I read an article about pyramid training and I think the idea is to fit it as many reps as you can while still pushing the weight. You change the reps according to the weight you are using. The higher the weight, the lower the reps. The idea here is that if you are pushing heavy weight, you can't do as many reps. So as you climb the pyramid, you increase weight and decrease reps. training like this allows you to do 60 reps instead of the typical 35 or 45 reps (three sets of 12 or 15).
Does that make sense?