This strategy will win, but it’s not accurate. Three 9s has the same effect as one 10. A 7 is a dealer advantage card. The 5 is the absolute worst card in the deck because it’s the only card that converts all 5 stiff hands into pat hands. A 5 is much worse than a 2, but your strategy gives them both the same value. It’s also necessary to keep a separate count of Aces. If your true count tells you to take insurance, it might be still the wrong play if the deck is Ace rich. Also, your playing strategy will be effected if the deck is Ace rich, or Ace poor etc. it’s especially important when doubling on 10. You will do it more often when the deck is Ace rich. Especially double 10 vs a 10 or Ace when have made bigger bets. It’s important to get as much accuracy as possible because the player advantage in blackjack the way it’s dealt today is very small, making the risk of ruin greater. But it’s most important that you play whatever strategy you use perfectly with no mistakes.