Per zone is fine. But it really does make sense for fixed schedules if one is trying to tune them because flex schedules don't work due to watering restrictions or such.
Right now my gardens are apparently super saturated according to the moisture level chart. Not sure why and it really does not matter since looking at the dirt tells me otherwise. But I might be overwatering. If I reset the moisture I can watch the effects of my watering schedule--fixed or flex.
(There is a good chance that the flex schedule did not work because of the assumed initial moisture levels. Once things are in balance with reality I will try it again.)