-51.95% is the change from 256 to 123
Calculation steps:
[( 123 - 256 ) ÷ 256] x 100 = -51.95%
Formula
Percentage change = [(123 - 256) / 256] x 100
Subtract the new number by the original number
123 - 256 = -133
-133 ÷ 256 = -0.51953125
-0.51953125 x 100 = -51.95%