21.57% is the change from 255 to 310
Calculation steps:
[( 310 - 255 ) ÷ 255] x 100 = 21.57%
Formula
Percentage change = [(310 - 255) / 255] x 100
Subtract the new number by the original number
310 - 255 = 55
55 ÷ 255 = 0.21568627450980393
0.21568627450980393 x 100 = 21.57%