The simple physics
Tens and Aces make blackjacks (which pay 3:2), improve doubles, and make the dealer bust stiff hands more often. Low cards (2–6) help the dealer’s weak upcards complete. If more high cards remain than usual, the shoe is good for you.
What counting estimates
You are not memorizing every card. You keep a running score of whether the remaining shoe is rich in high cards or low cards — then bet more only when it is rich.
Think marathon, not magic.
Tip: Counting does not make every hand a winner. It shifts the odds slightly in your favor over many hours when combined with correct strategy and bet sizing.