It's a rig. For every 4.95 hours of your line you get an hour's pay. That total or your block and DH time, whichever is greater, is what you get paid. You may have a 17 day line but if the trip leaves at 12z on day one and ends at 12z on day 17 you have (16x24)/4.95=77.57 hours pay. If iyour line only 15 or 16 days it will be less.