Power Commander explained

Q. I’m thinking of getting a Power Commander III. What is the “accelerator pump feature”?
 
A. This feature is built into all PCIII USB and PCVs, it allows you to configure settings which inject a small amount of extra fuel during fast throttle openings, this stops the bike hesitating when the throttle is snapped open and is particularly effective on big V-twins like Ducatis and Harley Davidsons.

The best place to start is with the suggested setting from the installation guide and then go out and ride the bike, see if it compliments your riding style.

If desired you can then try fine-tuning the sensitivity setting. Try starting at 90% sensitivity and then testing the bike at 5% intervals. There are no magic settings and it is very much down to individual preference.