Set Change to indicate the number of units between Min and Max the Position moves whenever the user clicks on one of the arrow buttons. Change represents the mapping between the units used to specify Min, Max, and Position, and the logical units represented by the scroller. 

For example, if the values of Min, Max, and Position are given in screen pixels, Change would be the number of pixels to scroll whenever the user clicks the scroll arrow. 

Max 

Min 

Position