When i do this i nock an arrow. Then line the arrow up with the horizontal line. That puts the bow pefectly square with the grid. The i line a bow tip up with one of the verticle lines. This shows me if the other, usually the lower, tip is forward or aft of the upper tip. The benefits there are self obvious, knowing which limb is stronger. Add the that you can put a 6 inch scale on the screen and take measurments to see where each limb needs adjustment. Also, you can lay tracing paper over the screen and draw one limb, then flip the paper to superimpose it over the ither limb, to check symetry. That can also be done through an app, but its too complicated for me, my wife does it when I ask her.
