-31.14% is the change from 928 to 639
Calculation steps:
[( 639 - 928 ) ÷ 928] x 100 = -31.14%
Formula
Percentage change = [(639 - 928) / 928] x 100
Subtract the new number by the original number
639 - 928 = -289
-289 ÷ 928 = -0.3114224137931034
-0.3114224137931034 x 100 = -31.14%