PC-DMIS uses the first two calibrated slots to calculate the "safety plane". If X+ is the actual orientation of the probe changer, and if slots are at different X values:
You must calibrate as slot 1 the garage that sits behind (X=X1).
You must calibrate as slot 2 the garage that sits in front (X=X2).
Or, vice-versa.
The TCRackClearance value is then added to X3 = MAX(X1, X2) to obtain the distance that the arm moves in +X (or -X) after and before the probe drop-off sequence is performed.