I have noticed small differences in basic strategy charts for the same rules. For instance, in Norm Wattenberger's "Modern Blackjack - Free Version" here is the suggested play for 2D, HS17, DAS, NS: 66 split thru 6 and 77 split thru 7.
However on "Blackjackinfo.com" using their basic strategy generator for the same set of rules, the suggested play is: 66 split thru 7, and 77 split thru 8.

Here is another: Modern Blackjack A8 v 6 is stand, but Blackjackinfo A8 v 6 is double.
And another: Modern Blackjack 9 double 3 thru 6, but Blackjackinfo is 9 double 2 thru 6
And another: Modern Blackjack 12 stand on 5 and 6, but Blackjackinfo is 12 stand on 4 thru 6

I would think that mathematically speaking, there could be only one correct basic strategy for any given set of rules but I run into these slight variations and it is confusing to me.

Would someone please explain how this happens and let me know where I can find the most mathematically correct basic strategy for 2D, HS17, DAS, Double any 2 cards, No Surrender.

Thanks

PS Norm, if you happen to read this post, you might want to make a slight correction on a tab heading. Chapter one, sample reco chart for HTML Two Decks, H17.
The chart shows up as that but the tab at the top when you click on it shows 6D, S17, DAS. Just a small misprint I noticed. By the way, your book is great and CV is fantastic. Thanks for both of them. Johnny