20.7% is the change from 256 to 309
Calculation steps:
[( 309 - 256 ) ÷ 256] x 100 = 20.7%
Formula
Percentage change = [(309 - 256) / 256] x 100
Subtract the new number by the original number
309 - 256 = 53
53 ÷ 256 = 0.20703125
0.20703125 x 100 = 20.7%