Settings
Unless you're referring to setting the distance for a perfect shop head.
I usually hold the rivet next to the gap and adjust about one size under full length.
You're eye will learn and very soon, you will guess very close.
If you have different lenths to set, count the turns so you can get back to the perfect setting.
Also, keep in mind the setting will vary with the size of the yoke used. The biger ones give a little.