-98.6% is the change from 641 to 9
Calculation steps:
[( 9 - 641 ) ÷ 641] x 100 = -98.6%
Formula
Percentage change = [(9 - 641) / 641] x 100
Subtract the new number by the original number
9 - 641 = -632
-632 ÷ 641 = -0.9859594383775351
-0.9859594383775351 x 100 = -98.6%