The Heat and the Knicks are basketball, not baseball.
I am not sure how one would bet on baseball. But in football and basketball, you can bet based on the point spread, which is the most common way of betting.
That is what the "5.5" means. The Heat are "getting" 5.5 points. Their opponent would be "giving" 5.5 points. That means that the final score for the Heat would have 5.5 points added. Then the winner of the bet could be determined.
If the Heat win the game, then adding 5.5 points makes no difference. If you bet on the Heat, you win the bet.
If the Heat lose the game by 1-5 points, and you bet on them with the 5.5 points, then you win the bet. Even though the Heat lost the game.
If the Heat lose by 6 points or more, you lose the bet.
(The half point in the betting line is so there are no "ties" in the betting. Since there are no half points in the game.)
I am not sure what the other "six to five" expression means, but it may mean that you need to bet 6 dollars to win 5.
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