If you've ever seen a betting option with a . 5 (like will a quarterback throw more than 2.5 touchdowns), this doesn't mean half of a touchdown, this is so a sportsbook can eliminate the possibility of a push. Two touchdowns is less, three touchdowns is more  meaning this bet either wins or loses.

On the other hand, an "over 2.5" bet means that you are betting that there will be more than 2.5 total goals scored in the match. This means that the bet only wins if there are 3 or more total goals scored in the match. If there are exactly 2 goals scored, the bet would be a loss.