The wager is based on the position of the horse, in the leaderboard, at the end of the race.

Example:

 If the over/under is 3½, and the horse finishes in the top 3 then the under is the winner, if it finishes 4^th or lower, then the over is the winner.

If the over/under is 6½, and the horse finishes in the top 6 then the under is the winner, if it finishes 7^th or lower, then the over is the winner.

If the over/under is 7½, and the horse finishes in the top 7 then the under is the winner, if it finishes 8^th or lower, then the over is the winner.

If the over/under is 8½, and the horse finishes in the top 8 then the under is the winner, if it finishes 9^th or lower, then the over is the winner.