It’s just the brake clearance specs for work wheels.
Disk Type:
・A disk - Standard brake clearance
・O disk - Small brake clearance with deep rim
・L disk - Big caliper brake clearance
・R disk - Big caliper brake clearance
I’ve since found out that for R32 GTR you’ll need R-Disk to clear front brakes without spacers and rear can be O, A, or R disk.