-87.94% is the change from 821 to 99
Calculation steps:
[( 99 - 821 ) ÷ 821] x 100 = -87.94%
Formula
Percentage change = [(99 - 821) / 821] x 100
Subtract the new number by the original number
99 - 821 = -722
-722 ÷ 821 = -0.879415347137637
-0.879415347137637 x 100 = -87.94%