-30.77% is the change from 923 to 639
Calculation steps:
[( 639 - 923 ) ÷ 923] x 100 = -30.77%
Formula
Percentage change = [(639 - 923) / 923] x 100
Subtract the new number by the original number
639 - 923 = -284
-284 ÷ 923 = -0.3076923076923077
-0.3076923076923077 x 100 = -30.77%