When the dealer shows a 4, 5, or 6 in Blackjack, it’s considered a weak upcard, and players should adjust their strategy accordingly, as the dealer is more likely to bust with these cards. If you have a hand totaling between 12 and 16, it’s typically best to stand, as the dealer is at risk of busting, and you don’t want to risk going over 21 by drawing another card. If your hand totals 9, 10, or 11, doubling down is a strong option, especially against a 4, 5, or 6, as you have a good chance of improving your hand while the dealer faces a higher risk of busting. With a soft hand (such as an Ace-2 or Ace-3), you should generally hit if the total is between 13 and 18, since you have a lower risk of busting and can try to improve your total. If you have pairs like 2s, 3s, or 6s, it’s often wise to split them against the dealer’s weak cards to maximize your chances of winning. Surrendering, if available, is generally not recommended when the dealer shows a 4, 5, or 6, as the dealer’s vulnerability increases your chances of winning. Overall, the key to playing against a dealer with these cards is to be conservative and take advantage of the dealer’s high probability of busting.