-21.92% is the change from 821 to 641
Calculation steps:
[( 641 - 821 ) ÷ 821] x 100 = -21.92%
Formula
Percentage change = [(641 - 821) / 821] x 100
Subtract the new number by the original number
641 - 821 = -180
-180 ÷ 821 = -0.2192448233861145
-0.2192448233861145 x 100 = -21.92%