Bill: How much does - gain? At the end Black has 1/3 point for the stone in ko (). (Black will have to protect against the cut at a.)
Bill: Note that Black cannot reply at , because threatens Black's group on the left. (See Endgame Problem 31.)
Bill: If Black plays first he gets 2 points (). (He will still have to protect a.)
The original count in the 2x6 region is 1 1/6 point for Black. Each player can gain 5/6 point in gote.
Since there are plays on the board that gain 1 point, - is a small technical error. It does not change the result with otherwise correct play.