Correct, one hour before the flex schedule would run, we check the current moisture level along with predicted precipitation for the day (and predicted moisture depletion), and determine if the moisture level is depleted enough to run the flex schedule.
If you navigate to a zone and tap on 'moisture level' you will see a graph that shows predicted days when it will run. (the webapp app.rach.io is easier to visualize this data)
It is a very complex problem which we are trying to make simple. These questions are great. Early next Spring (before watering season) we will do a major release that hopefully simplifies a lot of things. Currently flex schedule duration is easy to adjust, but not necessarily the frequency.
This article has some basic tips if you want to make slight adjustments to the flex schedule frequency (or duration) and might help understand some concepts.
My goal for next year is to not have the average user (unless they want to) have to understand field capacity, allowed depletion, etc.
Love it, I was in the same boat, there is a science behind it, great to see other passionate users.