-98.6% is the change from 642 to 9
Calculation steps:
[( 9 - 642 ) ÷ 642] x 100 = -98.6%
Formula
Percentage change = [(9 - 642) / 642] x 100
Subtract the new number by the original number
9 - 642 = -633
-633 ÷ 642 = -0.985981308411215
-0.985981308411215 x 100 = -98.6%