-68.78% is the change from 820 to 256
Calculation steps:
[( 256 - 820 ) ÷ 820] x 100 = -68.78%
Formula
Percentage change = [(256 - 820) / 820] x 100
Subtract the new number by the original number
256 - 820 = -564
-564 ÷ 820 = -0.6878048780487804
-0.6878048780487804 x 100 = -68.78%