399.5% is the change from 200 to 999
Calculation steps:
[( 999 - 200 ) ÷ 200] x 100 = 399.5%
Formula
Percentage change = [(999 - 200) / 200] x 100
Subtract the new number by the original number
999 - 200 = 799
799 ÷ 200 = 3.995
3.995 x 100 = 399.5%
Example