It's a two step process. First rotate the crank until the points are open at it's widest. Then adjust the gap to 0.3~0.4mm. Then rotate the crank to the point where the points >just< open the 1.4 plate should be rotated so that when the points >Just< open, the 1.4 F mark (the tick not the letter) aligns with the notch.
Same process with the 2.3 set; adjust max gap, and then move the subplate up or down to mak the points >just< opens when the 2.3 F mark aligns with the notch. A small 12 v lamp with two wires and alligator clips works fine for this. Clip across the points. turn on ignition. The light will come on when the points are open.
Cheers,