DVC is sold as a percentage of a “Residential Unit” in the specific resort, with that ownership represented as points. What constitutes an RU varies per resort - at OKW, each building is an RU, at BWV the RUs are composed of varying sizes of villas, at VGF BPK there are 2 RUs that together encompass the entire building.
When DVC sells a contract, it can come from one and only one RU. So if they have a customer who wants a large contract, for instance, they sometimes don’t own enough of a single RU to provide the points they need. So they might ROFR a resale because of the RU those points come from.