-39.57% is the change from 647 to 391
Calculation steps:
[( 391 - 647 ) ÷ 647] x 100 = -39.57%
Formula
Percentage change = [(391 - 647) / 647] x 100
Subtract the new number by the original number
391 - 647 = -256
-256 ÷ 647 = -0.3956723338485317
-0.3956723338485317 x 100 = -39.57%