-99.4% is the change from 999 to 6
Calculation steps:
[( 6 - 999 ) ÷ 999] x 100 = -99.4%
Formula
Percentage change = [(6 - 999) / 999] x 100
Subtract the new number by the original number
6 - 999 = -993
-993 ÷ 999 = -0.993993993993994
-0.993993993993994 x 100 = -99.4%