This GridOption is used if the current Template contains schedule hour tokens of the form [h1]..[h24]. It allows you, using the exact same GridTemplate and scanned template, to determine the schedule hours for different diaries' editions.
For example you may wish your German diaries to start (ie. first hour of the day) at 7am, but other editions to start at 8am. You can even have the schedules start at different times on every single day, which is often the case for week-ends.