Hoyt bows with fall away rests often tend to shoot well if the bottom of the arrow is about centered with the Berger hole. With other rests, though, or other bows, middle of the arrow going right across the middle of the hole is a good starting place. I also like to start with the center of the arrow about .780 from the shelf, as a good starting place for horizontal adjustment. I am not sure as to the exact reason for the recommended nocking point being a little above square; but I have always had to be a little above this point to get the bow to tune properly.