As rainfall amount varies significantly even in a small area, the weather data could be not accurate enough for your place. Netro still watered your zone after heavy rain, this might because the weather forecast said there was going to be a small rain but it turns out to be a big one. The soil moisture level will not increase a lot after small rain so Netro still watered your zones to keep the soil mosute level up. You can go to the Home page, tap the moisture level(%) in a circle in the zone area to check the soil moisture level of your zone by week/month.
Of course, all weather forecast could be wrong. Netro tries the best to provide accurate watering schedule even with incorrect forecast. First, we periodically update the weather data, once the weather data is changed, we update the un-executed schedules ASAP. Second, we re-check the weather data for the past, update our model, and adjust following schedules accordingly. For example, Netro may not water today due to large rainfall from forecast data. The next day, Netro re-check the weather data, if no rainfall found and your soil is dry enough, Netro will water accordingly.