-98.59% is the change from 639 to 9
Calculation steps:
[( 9 - 639 ) ÷ 639] x 100 = -98.59%
Formula
Percentage change = [(9 - 639) / 639] x 100
Subtract the new number by the original number
9 - 639 = -630
-630 ÷ 639 = -0.9859154929577465
-0.9859154929577465 x 100 = -98.59%