Bill,
While arrow attitude in the bale is important for some, there are times when you will get a false reading. This is due to the grain, density, and material used in bare shaft tuning.
The shooter should be directly in front of the butt, and the butt should be level with the shooter for best results.
However the most important factor is what the arrow is doing in flight. Ken Beck says that there may be times, due to release, and other factors directly related to the shooter, that you might not get the perfect flight.
He suggest that you get the best flight you can, and he very seldom focused on what the arrow did after it hit the bale, but how the arrows attitude was in flight. That is where the attention to nock left, nock right, nock high, or nock low should be focused.
This is just my opinion, and I know there are others how do not share it. If it helps great, if not, toss it in the trash. Good shooting to you all!