Bulzeye, the chart has noting to do with selling more arrows. In fact, just the opposite. You make a selection from that chart and you have the correct arrow spine for your particular set up. Your arrow purchase will match your cam, draw weight and length. It's when a shooter considers speed is more important the accuracy that a set up is hard to tune, if at all, and are alway having problems with stings, cables, noise and limbs because of shooting arrows too light for their particular set up.