-39.28% is the change from 639 to 388
Calculation steps:
[( 388 - 639 ) ÷ 639] x 100 = -39.28%
Formula
Percentage change = [(388 - 639) / 639] x 100
Subtract the new number by the original number
388 - 639 = -251
-251 ÷ 639 = -0.39280125195618154
-0.39280125195618154 x 100 = -39.28%