The contract is 17 days and can be extended to 20. The rig covers working days but not recurrent or vacation. So I had 9 days flying and 8 days in MIA one month. One vacation cut a month to 9 flying days this spring. Last month's vacation cut the flying to 13 days but I should be paid for 3 days of vacation that fell outside of work. And one month a 11 day trip evaporated and turned into home reserve - no rig or per diem. I got called out a couple times for 3 day hops, at the end of the month I was out 13 days.
As pointed out above, the you get an hour's pay for every 4.95 hours away from base. So a full day on the road is 4.84 hours pay. But if your trip starts at noon you're only going to credit 2.42 hours that day. And if your trip gets you back to your base at 18:00, you'll get 3.63 hours credit for that day.