Keith
If hole #1 is .250 +/- .005, and hole "B" is .250 +/-.005, and hole "C" is .500 +/- .005, let us say that hole #1 is .251 you get to add .006 to your first MMC, and if hole #2 is .245 you do not get to add any thing to your tol., and if hole #3 is .505 you get to add .010, so your call out is .010,+.006,+.000, +.010, so your positional zone is .026, with MMC the smaller the hole the less you get to add to your tol.
I hope I under stood your question right and this helped, If you have any questions you can call me at (916) 638-3344 x220

John D. Ruys
CMM Programer/Inspector
Teledyne MEC
Rancho Cordova CA.