It will vary. Start at 7 3/4. If the arrows are kicking right, increase it 1/4". If kicking left, decrease by 1/8". If they are kicking up then lower your nock 1/8". If it gets worse, then raise it by 1/8" until you get a good arrow flight. If you are shooting split fingers, the nock should be close to 3/8" to 1/2" above the shelf.

Best of luck.