In number theory four is the first number. I doubt this is what Pauls had in mind when he came up with his seven Phases but you never know. I can't really know why he always had to land on seven but can say with certitude that he had some sense of 'specialness' about seven. I can speculate that it traces back to his Mennonite background with its seven sacraments.
Every time he came 'round to the San Francisco Bay Area I would go study with him and he would give a different accounting of what the phases meant to him. I can only assume he told other versions at the other stops in his mapping.
The Gospel(s) According to Pauls
From Shivambu Kalpa:
Phases 1 to 4 These are gradual changes to the original Jones work but done with less time than his which took 90 seconds for uniform correction. Some of the Phases 4's [sic] can be reduced to 10 seconds.
From The Philosophy and History of Ortho-Bionomy:
Phase One
Phase Two
Observation: I keep hearing the same word screaming in my ear while I am doing Phase One: Boring! Boring!! BORING!!! Why? Why always three times? Why? Why?? Why??? Can't we turn work into play? Maybe there would be some fun! Fun!! FUN!!! in it. But the idea is childish. Who would seriously listen to a child?