If you turn on the smart zone feature, Netro will skip the schedules(including manual schedules from user programs) when there is a chance of significant rain. You can customize the weather restrictions to adjust the rain threshold as currently the value is 0.4 inch which is high, you can adjust it to 0.2 inch.
Netro gets weather forecast data from our weather provider, which could be not accurate enough, as weather forecasting is chanllenging. You can check the weather data on the home tab. If it is not correct, you can select other weather provider in settings->weather provider. You can also select the weather station ID with the Wunderground option. You can also adjust the rain data through Discover page->"+" button on the upper right corner-> Correct rainfall.
The rain delay is to forbidden watering in the next n days after rain, where n is set to be 5 by default. After you set the rain delay, Netro will update the watering schedules automatically, which can be checked on the schedule page. You can also find the constraint added.
If you go to the "rain delay" again, Netro assumes you want to add another "rain delay" constraint, instead of showing the last rain delays.
To cancel reain delay, you can go to your schedule tab. The date with gray dot beneath is the date with restriction/weather skip. You can select the date, and tap on the specific restriction, it will pop up option for you to cancel.
Please note that rain delay is just one-time setting. It's mainly used when it's raining but the weather forecast data is incorrect, so you can tell Netro that I don't want watering in the next n days. If the weather data is correct, Netro will not water while raining. You should set in settings->preferences -> rain -> days to skip, if you want to set it for all rainy days.