What I read is that if you had, say, the 6-7 person rate for your trip because you had 6 people, and one person cancels, so you now have 5 people,
ABD reserves the right to charge you the 4-5 person rate instead of the 6-7 person rate.
The verbiage from the ABD website is:
And I can understand this. If the price per person were locked when you book, someone might get 4 friends to sign up with their family of 4, and they'd get the 8-12 person rate. Then the other 4 could cancel prior to 14 days, and get their deposits back, but the price per person is locked. Since the rate is tied to the number of people (NOT a price for the entire group), I totally understand that ABD would do this. They're just trying to protect themselves.
Personally, before I signed up for anything, I'd ask to get it in writing from ABD how that works. I would never give them carte blanche to charge whatever they want if someone cancels. They need to be more specific as to how that increased price would be derived, and what the limitations on the increase would be.
Sayhello