20.78% is the change from 255 to 308
Calculation steps:
[( 308 - 255 ) ÷ 255] x 100 = 20.78%
Formula
Percentage change = [(308 - 255) / 255] x 100
Subtract the new number by the original number
308 - 255 = 53
53 ÷ 255 = 0.20784313725490197
0.20784313725490197 x 100 = 20.78%