mrbb is right. The points of impact will need to be figured out by seeing where your arrow/broadhead combination hits. Your set up will be different than mine would be. I'd set the center crosshair at 20 yards and then start shooting and see where the second crosshair hits. May be 30 , 33, 36 or 39 yards, who knows. But, do this with the arrow and head you plan to hunt with. I use 3 bladed Muzzys and remove the blades when sighting in. Once I'm dialed in I then put a set od old blades in to get things precise. The practice blades that comes with Muzzys don't fly the same as the actual razor blades for me.

And strings do wear out quite often. And when one is replaced everything will be off as far as scope settings. You will need to start all over. I use a 3-9 Bushnell scope on my Horton, but I only take shots at 20 yards or less. I like the magnification for checking antlers on bucks at longer ranges.