The "seventh" row consisting of four pins is for an I2C data connection, not an endstop. There are six endstop connections. Each axis can have an endstop at the min travel and/or at the max travel. Most use just the min travel endstop, but a printer can be configured to use either or both.

Board markings have been reported to vary, depending on the source of the board. On my MakerFarm Prusa i3 RAMPS, the min travel endstops were connected to the rows of pins marked X-, Y-, and Z-, which I think were your positions 1, 3 and 5.