People seem to call them Nav Cards, and as far as I know, they have no use at the moment. If you don't already have it, you can find it beside the Bus Depot. If you just opened the doors, go as far as you can left and hug the building. After you turn a corner, keep going, and there should be a small area with pretty much nothing in it. The Nav Card is somewhere around there. =p IIRC you can't pick it up if someone else in the game already has it, so you'll probably want to do it solo.
Are you sure that YOU have two? More than one person in a game can have them, and they show up beside whoever has one's points. You might just be mistaking it for other people in the game having them. I've never heard of someone having two before. o.o