In general, for the tightest loop control, the dynamic controller gain should be as high as possible without causing the loop to be unstable. The process is typical with a dead time of 4 and lag time of 10. Optimal is red. You can use the picture to recognize the shape of an optimally tuned loop. Also see the response shape of loops with I or P too high or low.
P is in units of proportional band.
So increasing P or I, decreases their action in the picture.