If you just play fitness ball, you can play as many rounds as you want. If it is a game, the number of rounds is determined by the level of both players. If the two are evenly matched, it will take more rounds, otherwise we will know in one or two rounds. Badminton is usually the best of three games, with 2 1 point per game. Whoever gets 2 1 point first wins.

Badminton competition rules: 1, 2 1 points system, 2 wins in 3 matches is the best. 2. The scoring system of each ball. 3. In each round, the winner will get 1 point. When both sides score 20 points, the one who leads the other side by 2 points wins. 5. Both sides scored 29 points, and the one who scored 30 points first won. 6. The winner of one game takes the lead in serving in the next game.