-99.4% is the change from 500 to 3
Calculation steps:
[( 3 - 500 ) ÷ 500] x 100 = -99.4%
Formula
Percentage change = [(3 - 500) / 500] x 100
Subtract the new number by the original number
3 - 500 = -497
-497 ÷ 500 = -0.994
-0.994 x 100 = -99.4%
Example