100.39% is the change from 255 to 511
Calculation steps:
[( 511 - 255 ) ÷ 255] x 100 = 100.39%
Formula
Percentage change = [(511 - 255) / 255] x 100
Subtract the new number by the original number
511 - 255 = 256
256 ÷ 255 = 1.003921568627451
1.003921568627451 x 100 = 100.39%