The 15 day schedule during a vacation period means you have 7 days of vacation and 8 remaining days of work. 7 + 8 = 15. You can only work 5 days at a time, except training. Most likely, you will get 2 tours that are 4 days long.
If you have vacation and training (7 days total including 2 travel days) in the same month, and training does not overlap two months, you will likely not be used for your one day.