Sometimes I have been in the situation where I needed to pull 4 12/2 w/G's in the blue box to connect to other circuits. I only count all the grounds 1 time, each individual conductor 1 time, the yoke (switch or receptacle) 2 times and each wire nut (clamp) 1 time.
As mentioned above, wire nuts are not clamps. See 314.16.
Clamps attach the cable to the box, not conductors together.
The easiest way to keep these things straight when first getting them straight, IMO, is to go down the list one by one:
So 4 12-2's with 1 device are
8 insulated conductors
0 Support Fittings
2 counts for 1 device
1 count for all EGC's
Is 11 conductors x 2.25 = 24.75 cu.in.
That's way over for a single gang, even Carlon. (gfret, box fill is something best understood when the same math is done four different ways.