The /- 3/64” tolerance is applicable to the manufacturer’s net dimension. The net dimension may vary depending upon the manufacturers’ design, i.e. beveled hinge and lock edge, beveled lock edge, square hinge edge, or square hinge and lock edge. For a manufacturer with a beveled hinge and lock edge design, the math would look like this: A door is ordered at a nominal width of 3’0”; The net width of that door will be 35 13/16” The 3/64” tolerance means it can be 35 55/64” (widest) The - 3/64” tolerance means it can be 35 49/64” (narrowest) Even at the narrowest dimension, it would still be within the NFPA 80 tolerance of 1/8” on both sides—36.000 minus .125 (x 2) equals 35 3/4”. In SDI-117, figure E in section 5.1 the dimensions are based on the NET door width. In figure B of section 4.2 there are the dimensions and tolerances for the frame.