The video shows how the voltage output from the anti-rollback / anti-tipping / anti-spilling potentiometer works with the controlling voltage on the electronic servo actuator on the hydraulic valve for the Bucket function on the front loader.
The joystick sends a neutral signal of 50% voltage to the valve (6,4v in this video) when untouched. When the potentiometer sends a signal below this it overrides the signal from the joystick, making the bucket tilt downwards.