Your reply about going in after PTP sounds confusing, but I
think you got it right.
Here's a real-life example. Dates are not very accurate, but
roughly.
John enlisted around late Feb 2000. He PTP batch one. I enlisted on
April 5 2000, non-PTP batch. We POP on same day, around June 10.
And we go same unit.
Fast forward ...
I ORD on Aug 4 2002 (2 year 4 months). John ORD on Aug 22, 2002 (2
years 6 months).