Blackjack What does 2.5 mean in tennis betting?

In any tennis game bookies will allow you to bet on the total number of sets played, this is often displayed as a 2 way market. For example, a bookie may offer over or under 2.5 sets in a game, if you bet on over 2.5 sets and there are 3 or more sets played then you win.
Tennis matches are made up of sets and games. Each player will serve a game, and this will alternate between each player in every game. In each game the first player to reach a game point or 5 points. Scoring in a tennis game works like this 0, 15, 30, 40 then a game. To win a game you must win a game point and be 2 points clear of your opponent, but if both players are on 40 points, you must win 2 points in a row to win. This situation is often referred to as a deuce; it’s then scored as an advantage and then a game point. Each player must then win six games to win a set, but a player has to win by two clear games to win a set. If a player is not two games clear once he has reached six then one more game can be played and if he is two clear the player has won the set. If the set is drawn 6-6 then the set must go to a tiebreaker. A tie-breaker is a game that is the first to 7 points, but again a player must be 2 points clear, so a tiebreaker will be played until a player is 2 points clear. To win the match, you must win 2 or 3 sets depending on the tournament (although it is always two sets for women).
There is one exception to the tie-breaker rule, if a set is drawn in a final set in a major tournament then it cannot be won on a tie-breaker. Any player must win by two clear games to advance and win the match.