With the duet, there are 3 winning payouts so the total pool is split in 3 for each of the winning possibilities.
This pool is then divided by the number of winning tickets.
In the race in question, there was a total of $360 only in the duet pool. That means there was only a total of $120 to be paid out for your combination. i would seem that there must have been $6 wagered on that duet combination