The RAW (Readily Available Water) line represents the amount of water in the soil, above which the plants will be in a non-stress condition.
It is OK to let the Soil Water Content drop below the RAW line in order to apply stress on the plants as needed by the implemented agro-technic.
The system will provide an alert once the Soil Water Content is getting close to  the WP (Wilting Point) line, which might result in permanent damage to the crop.