-99% is the change from 400 to 4
Calculation steps:
[( 4 - 400 ) ÷ 400] x 100 = -99%
Formula
Percentage change = [(4 - 400) / 400] x 100
Subtract the new number by the original number
4 - 400 = -396
-396 ÷ 400 = -0.99
-0.99 x 100 = -99%
Example