That's the way I understand it. You "owe" the company so many days when you have X vacation days. There was a chart out somewhere that showed how many days you had on call and how much you were paid for each week of vacation under PBS. Maybe on the APA scheduling page?

That's how you get paid more than guaranteed with vacation while on reserve. Your pro rate and vacation days add up to more days than usual.

Haven't been on reserve for a while, might try it this year during Sept to see if I can get most of the month off for 83 or so hours.