Instead of the default PAS 1-5, try 0-9. This will give you finer increments of PAS to suit you. Alternatively, you can reduce the max Current from the default 15A to 10A or less. This will limit the max power to the motor. 15A = 750W, 10A = 500W, 5A = 250W, etc.
Here is as much as I can...