Flex schedules work off of zone soil moisture level data. If the zones have not been watered through the controller they will essentially be empty, and the schedule will want to water the day after the schedule is built.
The duration that each zone will run is fixed, so will not matter if the system is off or on. The initial amount is just the amount used to fill the bucket so to speak and will be applied each time (no variance).
If you have any other questions just let us know. FYI flex will eventually be superseded by simpler scheduling.
