That's not precisely accurate, as up to a 12 hour duty day (as originally constructed within the bid package) is 1 minute of pay for every 2 minutes of duty, and then premium pay at 1 minute of pay for every 1 minute of duty for each minute after the 12th hour. The pay for a duty period is the greater of what you actually do, minimum daily guarantee (4 hours, 12 min, abbreviated MDG) or the duty or premium rig. See Standard Practice 3005 Definitions. Pairings are paid as the sum of the duty periods (including 4:12 for a lost weekend...like this one in International Falls) or the TAFB guarantee (1 minute of pay for every 4 minutes of TAFB), whichever is greater.
(Note that this is scheduled not actual, sadly, but it's the system we've got.)