@chinhster, I apologize for any inconvenience caused. Flex schedules are dynamic and can change pending reported weather data. You might prefer switching to Fixed schedules that are more predictable and do not dynamically adjust for weather.
Please note, we’ll be introducing new scheduling options this spring that marry the predictability of Fixed schedules with the intelligence of Flex schedules. For details, please refer to this community post. If you’d like to help beta test the new schedules, please sign up to do so here.
Flex schedules use the zone attributes provided to calculate the watering requirements of each zone. Vegetation type, nozzle type, and soil type have the biggest impact as they determine how big your soil reservoir (or gas tank) is via the root zone depth and holding capacity of the soil, then how long it takes to fill the gas tank via the nozzle’s application rate. If any of these inputs are incorrect, the watering durations will reflect the errors.
I can detail the math on one of your zones if you’d like, but I do believe our new schedules will address the concerns you have.