Power Scale acts as a sort of ‘slider’ between Min Power and Max Power. With a Power Scale of 100%, the output will be the Max Power setting. With a Power Scale of 0%, the output will be Min Power. 50% Power Scale will output 50% between Min Power and Max Power.
Note that this is all still subject to the rules regarding Start Speed and Min Power - If your speed is set at or below the Start Speed setting in the controller, you’ll only get Min Power.