The DMAs are made up by Neilsen, and are based on what city's channels each county watches most. Since cable in areas like that often carries multiple combinations of affiliates from multiple cites, the fringe counties can move from one DMA to another from year to year.
DBS has the option of accepting the new map, or freezing the map as is. Apparently in your case one has done the former and one the later.
DBS has the option of accepting the new map, or freezing the map as is. Apparently in your case one has done the former and one the later.