-99% is the change from 800 to 8
Calculation steps:
[( 8 - 800 ) ÷ 800] x 100 = -99%
Formula
Percentage change = [(8 - 800) / 800] x 100
Subtract the new number by the original number
8 - 800 = -792
-792 ÷ 800 = -0.99
-0.99 x 100 = -99%
Example