As it says right on the graphic, all you can do is catch up to the train in front of you. That means you can "make up" as most the headway between trains. Since the headway between trains is 6 minutes in the rush hour all you can make up is 6 minutes at best. Therefore you may skip up to N stops that would save you 6 minutes. Skipping all the stops would just have you waiting at the stations with your doors closed following a train stopping at every station.

WMATA is saying that skipping 7 stations is enough to gain that 5-6 minutes.

This won't happen. If it does it will get rolled back when the savings is not even 5 minutes on average.