This has always kinda bugged me, although it is not important functionally. I wanted to be sure I was clear (and maybe help anyone who is reading this to be clear).
SGP, refers to “step size” in the autofocus setup. To me, and most imagers I know, a “step” has always been one focuser tic. That probably came from “stepper motor” that some focusers use.
OTOH, unless I am mistaken, “step size” in SGP means the number of focuser tics (what I always called “steps”) between autofocus measurement exposures on the V-curve. Correct me if this is wrong but I think it is right.
For example, with my FSQ:
Physical step size is 1.2 microns (HSM motor), on the motor. The SGP “step size” 52. That means the focuser is moving about 62.4 microns between steps (samples) and over the 11 “step/sample” v-curve is moving about 686 microns.
I might suggest a different term be used to avoid confusion, especially for new users. I would suggest “focuser steps between samples” or something to that effect.