-98.6% is the change from 644 to 9
Calculation steps:
[( 9 - 644 ) ÷ 644] x 100 = -98.6%
Formula
Percentage change = [(9 - 644) / 644] x 100
Subtract the new number by the original number
9 - 644 = -635
-635 ÷ 644 = -0.9860248447204969
-0.9860248447204969 x 100 = -98.6%