How does the "SUB" work mode work?

Please be advised that this mode is only available for Pakistan users, it is suitable for application scenarios with frequent power outages. When the grid is operational, the load is powered by solar and the grid, and the battery only charges without discharging. With the grid available, the battery is generally kept at full charge. It only operates in off-grid mode to supply power to critical loads when the grid power is cut off. The load is primarily powered by solar, and if solar power is insufficient, the grid supplies power. In the absence of grid power, the system switches to off-grid mode, using the battery and solar to power the load. If the power generated by solar exceeds the load demand, the excess electricity is used to charge the battery. After the battery is fully charged, whether the surplus PV power is fed back into the grid or limited depends on the setting for zero-export at the grid interface.