-39.69% is the change from 640 to 386
Calculation steps:
[( 386 - 640 ) ÷ 640] x 100 = -39.69%
Formula
Percentage change = [(386 - 640) / 640] x 100
Subtract the new number by the original number
386 - 640 = -254
-254 ÷ 640 = -0.396875
-0.396875 x 100 = -39.69%