Its hard to get right the first time, so what I'v been doing to get them the same every time now that I have some I like is I loosen the thumb screws on the magnet & place a fletched arrow in the jig. Then I put the clamp over the feather on the arrow in the jig & t puls the magnet into place. f you need to adjust the nock setting you can loosen that thumb screw & turn the knob one way or the other until its not pulling on the vane or feather. Tighten the thumbscrews & your done.
If your arrow already has vanes on it I think Id set the jig like I described first & then refletch the whole arrow.