-99.6% is the change from 999 to 4
Calculation steps:
[( 4 - 999 ) ÷ 999] x 100 = -99.6%
Formula
Percentage change = [(4 - 999) / 999] x 100
Subtract the new number by the original number
4 - 999 = -995
-995 ÷ 999 = -0.995995995995996
-0.995995995995996 x 100 = -99.6%