(1) the height of the d is different too. With only the minimum and the maximum. Therefore, the adjustment to the mean value (2) a near minimum value .
(1) the height of the D values differ too much. There is a minimum and maximum value, and therefore help to middle-range (2) A value close to the smallest value
(1) the value of high-value D is different, too much is just the minimum value and the maximum, so you adjust the settings in the middle (2) the least A close.