I imagine it might be average data from people around you that might have sensor. These depend on shade, slope other factors but likely the value is correct most of the time. 

Hi Swaroop,

Netro's algorithm calculates the soil moisture level by taking a lot of factors into consideration: soil type, sprinkler type, manual watering, rainfall, weather information, evaporation and other factors and the moisture level impacts the watering schedules. After installation, we set the moisture level to be normal level (e.g. 75%) by default. This value is usually not very far from the real fact. 

Thanks,

Netro Support