-31.95% is the change from 939 to 639
Calculation steps:
[( 639 - 939 ) ÷ 939] x 100 = -31.95%
Formula
Percentage change = [(639 - 939) / 939] x 100
Subtract the new number by the original number
639 - 939 = -300
-300 ÷ 939 = -0.3194888178913738
-0.3194888178913738 x 100 = -31.95%