Shaw can expound more on this but charts are just to give you a good starting point. Ive seen 1lb of adjustment and 1/4" cut off an arrow make all the difference. I cant remember the exact arrow length on my bow but its a pretty random number. A "sweet spot" I found by trimming 1/4" at a time till it shot the way I wanted. Theres a lot more to "tuning" a bow than just turning a few allen wrenches, most people just never shoot well enough to notice the difference. Hell I dont either right now.