1-5-6-4 chord progressions wheel

This is an example of a song created by using the 1-5-6-4 progression from different starting points. I was particulary entertained by the coincidence that the last progression could be highlighted on the circle by using the greyed-out numbers which I had previously skipped in order to created/play the next chord progression in the sequence. The beat was programmed in FL Studio 9 inspired by Case and Foxy brown touch me tease me which was infact a sample of Schoolly D P.S.K what does that mean?