-98.61% is the change from 646 to 9
Calculation steps:
[( 9 - 646 ) ÷ 646] x 100 = -98.61%
Formula
Percentage change = [(9 - 646) / 646] x 100
Subtract the new number by the original number
9 - 646 = -637
-637 ÷ 646 = -0.9860681114551083
-0.9860681114551083 x 100 = -98.61%