Sorry, both of you were quick off the mark.
I did edit the post as i put the total micro steps in [ 800] instead of the number [4]

I did it pretty quick so that's probably why it didn't show

btw, i agree the maths is easier expressed as s x m / p, but I was showing how to get to that from first principles in stages...
So how do you express Ohms law in first principles ?