The measure at the bottom of the drawing is 58-5/8 and that is the wheelbase of the 101, so the measure 22-1/4 must mean from the center of the engine bolt to the wheel contact point on the ground. It's up to debate thou where the rear wheel axle is placed in the slot. Maybe in the middle. Or not. The fix point is anyhow the engine bolt.
I have been tubbing for YEARS all people that I know of that have the means to draw a BETTER frame drawing to no avail. HELLO anyone! I may be able to help with measurements but I don't have enough comfuser skills or/and them bloody programs!