-21.51% is the change from 823 to 646
Calculation steps:
[( 646 - 823 ) ÷ 823] x 100 = -21.51%
Formula
Percentage change = [(646 - 823) / 823] x 100
Subtract the new number by the original number
646 - 823 = -177
-177 ÷ 823 = -0.21506682867557717
-0.21506682867557717 x 100 = -21.51%