There is no first hour rule as there is with working into a rest day. The moment you pass 07.00hrs, the appropriate compensation applies.
Where there is uncertainty, and no clear answer, is what happens if the annual leave day is not part of a run of three days off? If you have booked a single day, the compensation described above does not apply. It is not a rest day, so that compensation does not apply either. There is no minimum four hours. We believe that you book overtime at time and one third, with no disregard of the first half hour, for only as long as you are on duty.