If I ignore vacuum for a moment it kind of fits, 12 initial + 18 - 20 = 30 - 32, would be 34 to 36 if I set 14 initial.
Did a little reading here (what do you think of this source?):http://www.gofastforless.com/ignition/advance.htm
and get that the vacuuum advance is a separate thing and to be treated separately once mechanical advance is properly set as desired.
Kind of makes sense except under partial throttle at or above the RPM when all mechanical is in. At that point the vacuum advance will provide even more advance and part throttle can be under load or not depending on what the car is doing (going uphill for example), so the vacuum part still seems somewhat confusing. Maybe the fellow even shows that the concept is not sound when he says that he had to take all but 5 degrees out of vacuum advance to get rid of pinging.
Then there is the ported vs. manifold vacuum source thing, I have always used ported.
So none of the total mechanical is to be subtracted and kept aside for vacuum, correct?
Still kind of confused about use and setting of vacuum advance.