I think for this exercise it was just to see if the bluff was profitable. Take his folding % and compare it to how often you need him to fold to show a profit.
if we 3b to 10bb in the sb vs a 3bb open we autoprofit if he folds more than 9.5/(9.5+4.5) or about 2/3. Because he's folding 88% we can profitably 3b atc.