I wish I would have known that before I got OnTarget. I must say, that setups vary so much, I would expect any program to be somewhat inaccurate. If someone has a lot on the string, or an odd draw length (slightly different string or cable length), dips their arrows, pulls extra hard into the valley or has some other factor that is not typical, the program would be off. It seems to me that a crono reading would be neccessary for real accuracy on any individual setup.