-98.6% is the change from 643 to 9
Calculation steps:
[( 9 - 643 ) ÷ 643] x 100 = -98.6%
Formula
Percentage change = [(9 - 643) / 643] x 100
Subtract the new number by the original number
9 - 643 = -634
-634 ÷ 643 = -0.9860031104199067
-0.9860031104199067 x 100 = -98.6%