020 is a reference the factory can give to the average Joe, without a Timing Fixture/Buzz Box combo to set their ignition. They can say, when the hole in the flywheel is over the points, set it at 020, or when the rub block is at the highest point on the cam, usually the crank keyway, set them at 020.

That does get you pretty darn close usually. Although, it doesn’t get them to fire exactly 180 degrees apart. Unless you are Spider Man!

Using the timing fixture, and buzz box (or multi meter, test light) will. Which in turn, gives the improved idle.

Richard, I am more experienced in OMCS. I believe, you could be referencing Mercs, which I know diddly about, so not sure how it applies.