OK, so using 7 outs on the turn and 10 on the river, the correct pot equity is 41% for the OESD + FD.

The calculation is as follows:

45*44 = 1980 possible turn and river combinations
14*34 = 476 ways to win on the turn without a boat or quads
24*14 = 336 ways to win on the river without a boat or quads

(476 + 336)/1980 = 41%

So his odds drop over 13% from the non-set case.