Where's the problem? A simple calculation reveals---
1) There are (3) 1/2" KOs. on each side of the box
2) There are 4 sides
3) That makes (12) 1/2" KOs
4) 1/2" thinwall is good for (9) #12 THWN
5) 9 x 12 = 108 #12s allowed in that box
6) I think there's room for 80 more.