Setting vacuum advance

The Allen Key adjusts the spring rate, so that the VA total amount does not fluctuate. Best to screw the AK fully CW [ softest setting ]. If the engine accepts that without light throttle ping, all is good. If it pings, the spring may need tightening [ AK, CCW ]...or....you might have too much total VA. Some experimentation will be reqd.

To limit total VA. Couple of ways to do it. If there is a marking on the VA arm, it is the amount of VA added in dist degrees. I did one last week, marked 10.5, which is 21 crank degrees. I wanted 17*. So I measured the movement of the arm & by proportion calculated the reduction in travel needed to give me 17*. Made a little metal stop to give me the correct gap & I silver soldered it to the arm, just before the bend in the arm to keep the heat away from the diaphragm.
Another way that you could limit VA travel is by limiting the movement of the plate with a screw or similar; haven't tried this but can see no reason why it would not work.
Long duration cams, single plane intakes, low CR, big carbs all want more cruise timing so 60* is not excessive with some combos.