-60.78% is the change from 255 to 100
Calculation steps:
[( 100 - 255 ) ÷ 255] x 100 = -60.78%
Formula
Percentage change = [(100 - 255) / 255] x 100
Subtract the new number by the original number
100 - 255 = -155
-155 ÷ 255 = -0.6078431372549019
-0.6078431372549019 x 100 = -60.78%