Mopar Performance Distributor adjustable advance?

Trial and error it is. I just set it in the middle. From what I (just) read it's adjustable from 0-28 degrees?! So half that should be 14, so I'll see what it does with timing at 20 degrees. I'll see if I can find these tuning keys. Anyways, the distributor came with the engine and I had never really looked at it. I'm glad I did.