A pawn on its second rank can move two squares, so its square is drawn as though it already stood on the third rank.
White's pawn is still on a2, and Black's king on g3 must decide whether he can stop it. A careless count says: a2 to a8 is six steps, the square a2-a8-g8-g2, and g3 is inside, so anything draws. That count is wrong.