In the draughts game, Walshy's opponent makes two moves before Walshy makes one. The position of the pieces at the end of the scene reflect a different game to the one they appear to have played, especially as they do not seem to have moved any pieces during their conversation other than the first three moves.
See behind the opening titles, the boys are running and they pass "Gray's" three times and "Weaver Too Wearer" twice.
When Walshy and one of his gang go to play draughts (checkers), the positions of the different coloured pieces seem to swap sides from when they approach the board (black on the left) to when they are seated (red on the left) to when they leave (black on the left).