-87.97% is the change from 823 to 99
Calculation steps:
[( 99 - 823 ) ÷ 823] x 100 = -87.97%
Formula
Percentage change = [(99 - 823) / 823] x 100
Subtract the new number by the original number
99 - 823 = -724
-724 ÷ 823 = -0.8797083839611178
-0.8797083839611178 x 100 = -87.97%