What counters do is reap the advantages of the continually changing odds in blackjack. In roulette or craps, the percentages are mathematically mounted to be the identical on every spin of the wheel or roll of the dice. In blackjack, the percentages turn in favor of the participant when an unusually large number of 10-value cards remain to be performed. When the deck is rich in 10s, the player will get extra blackjacks.