-39.56% is the change from 642 to 388
Calculation steps:
[( 388 - 642 ) ÷ 642] x 100 = -39.56%
Formula
Percentage change = [(388 - 642) / 642] x 100
Subtract the new number by the original number
388 - 642 = -254
-254 ÷ 642 = -0.3956386292834891
-0.3956386292834891 x 100 = -39.56%