These numbers are probably positional coordinates on the strategy map, like those you find for fort and port icons.
The third number (0 in most cases) I believe is the directional coordinate, like the one for ports.

However, changing them give no result in my experience, so as far as I know these numbers are not in use. Also, if you look in the viking invasion startpos you will see that all these numbers are set to 0.

My best guess is they are part of that "border fort" feature that we can find traces of throughout the game, but that were left out in the finished game.