As soon as your combo bet wins (minimum odds of 1.20 per bet), you will receive the combo bonus.

Here is how the combination bonus is calculated:

Combination of 5 -> 5% bonus on your winnings
Combination of 6 -> 10% bonus on your winnings
Combination of 7 -> 15% bonus on your winnings
Combination of 8 -> 20% bonus on your winnings
Combination of 9 -> 25% bonus on your winnings
Combination of 10 -> 30% bonus on your win