The "Hi-Lo" system is a card counting strategy used in blackjack that assigns values to cards to help players gauge the deck's favorability. Cards 2 through 6 are valued at +1, cards 7 through 9 are neutral (0), and 10s, face cards, and aces are valued at -1. Players maintain a running count based on these values as cards are dealt. A higher positive count indicates a greater proportion of high cards remaining, suggesting a better chance of winning. Players adjust their bets accordingly, increasing them when the count is high and decreasing them when it’s low to maximize their betting strategy.