> Looking at an 8D, S17 game, BS for 9v6 is D6.
> Table A5, with no modification for 8D in Table A9,
> lists the index for doubling 9v6 as -3. Is this due to
> rounding or a calculation error? Thanks.

Firstly: I'm looking at my book (page 15) and I see BS for 9 vs 6 as being D4, not D6.
No edition of my book has ever had D6 on this page for
It's not possible for the play to be D6 as there is no possible 6 card 9.

Secondly: The index for 9 versus 6 is -3. That is correct. On page 149, it talks about this. It's the same thing in Blackjack for 16 versus X. BS says hit, but if TC = 0, you stand.
The reasons why this is the case is that neutral count (-4 in SP21) is an average of all hands with this count, at the start, middle and end of the shoe. BS is just for the first hand. So just because the BS play is a double, it doesn't mean that the TC = -4 play is a double. It does MOST of the time, but not ALL the time.

Also: this is not in Table A9. It is Table A5. There is no 8-deck variation for 9 versus 6. Not in any version of my book, and not on the website.