1200 families would move into the 1000 units, of course.
There is a good piece of boilerplate on the general subject of overbooking in the DOt consent orders vs. airlines. By way of example, JetBlue Airways - Consent Order 2016-12-4
Being in the industry I’ve read that and it goes back to when people were booking seats on different flights but not actually paying for them until they arrive at the check-in desk so airlines were flying with empty non-revenue seats.