Its 500 group points.

As been said previously, it is mostly useless unless you just joined a group.

Many mechanics in the game are geared towards very large server population (i.e top 50 or 100 get to plunder, cheer for when there are more than 54 players in a team fighting in GNW, etc.). Unfortunately the huge number of new servers and the constant depopulation of older ones make those mechanics useless.