The "2-4-6" counting system in blackjack assigns values to cards to help players gauge their advantage over the house. Cards 2 and 3 are valued at +1, while 4, 5, and 6 are valued at +2; 10-value cards and aces are valued at -2. Players maintain a running count by adding or subtracting these values as cards are dealt. A positive count suggests a higher proportion of high-value cards remaining, indicating a favorable situation for the player, while a negative count signals an advantage for the dealer. Players can adjust their bets and strategies accordingly, increasing their bets when the count is positive and decreasing them when it is negative.