I'm not sure I'm explaining this well.
The pin on the weight moves in an arc.
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I *think* this usually makes it close to 1:1 relation with degrees when the arc is close to a 45 degree angle to the slots and the slots are perfectly radial like in the above distributor. I *think* when the weight is further in more movement is needed to advance the distributor and when its further out slightly more movement is needed to get a single degree of advance.
Angled slots certainly change the ratio.
Pin diameter and slop can effect the degrees as well. Some think that a little bit of side play between the slot and pin can be an advantage. I don't think these are super precise parts. So I think there is a degree of trial and error testing. No pun intended