The Tarken Glacier puzzle is a game of Dots and Boxes! Also known as Sticks or Dots-Squares or tons of other names.
The aim of the game is to makes boxes (squares) out of lines while not letting the other player (Computer in this case) gain boxes.
So the achievement was changed to win with giving up 2 or less squares. So now you need a 23 to 2 win for the achievement.
coords: 5979, 2960