1. Currently the minimum watering duration for manual program is 1 minute. If you want to water less than 1 min, you will have to go to the Home page, select your zones to water manually by tapping the blue button to do an instant manual run. I have talked to our R&D and we will support 30s' watering duration in future release of the app.
2. For the Smart Zone level basic. In this level, no smart schedule will be generated. It only depends on weather restriction(large amount of rain) or watering regulations. For more information about Netro smart watering, here is an article about Netro three watering modes which might be helpful. https://netrohome.com/forum/posts/111
3. If you select Add watering set for 50% to 1m in sensor's watering adjustment, it means Netro will start 1 minute watering when the moisture drops to 50%. However, there's not an exact date or time when the moisture drops to 50%. For example, if today the moisture drops to 50%, Netro will start watering for 1 min. However, if after a few hours today the moisture drops to 50% again, then Netro will water again because 1 min watering will not increase the moisture a lot.
We understand you need a shorter watering duration to avoid dripping onto your neighbour's balcony and I have forwarded your issue to our R&D. If you have any questions, you can reply to us or send us email to firstname.lastname@example.org.