I'm guessing that if the spark is cam triggered, it's probably done from a sensor on the cam gear itself. The adjustability would come from moving the camshaft in relation to that gear.
So the gear would be installed such that the spark even thappened at the correct time relative to piston position, and then you could adjust the camshaft to provide the advance/retard that you want.
I guess you could probably also use the adjustable cam gear to dial up ignition advance/retard if you wanted to. Just install the cam gear advanced or retarded from the crank gear, then dial in the camshaft adjustment to account for that too.
Of course all of this is if the spark is cam triggered. I seem to remember something about a crank trigger, but I could be thinking of a TEC-II.