Distributor curve. I agree it is best to know when it stops advancing. Also two points is not enough to know the shape. It may be a two stage advance. It didn't ping at WOT, so it was never too advanced at full load. The advance may slightly retard at higher rpm. Depends on the ignition box and distributor. Since your not turning it much past 5000 rpm at this point, I don't think its that important.