-39.05% is the change from 420 to 256
Calculation steps:
[( 256 - 420 ) ÷ 420] x 100 = -39.05%
Formula
Percentage change = [(256 - 420) / 420] x 100
Subtract the new number by the original number
256 - 420 = -164
-164 ÷ 420 = -0.3904761904761905
-0.3904761904761905 x 100 = -39.05%