The Integral Gain controls the response to speed error over time. A greater amount of time spent not at target speed will cause an increasing throttle response. Integral Gain is necessary to properly achieve your target speed, as acts to fully eliminate any error over time. A higher Integral Gain will result in a faster throttle response, though too high will cause overshoot of the target speed. 

The values in this table are dependent on your speed units selected in Preferences.