-30.66% is the change from 923 to 640
Calculation steps:
[( 640 - 923 ) ÷ 923] x 100 = -30.66%
Formula
Percentage change = [(640 - 923) / 923] x 100
Subtract the new number by the original number
640 - 923 = -283
-283 ÷ 923 = -0.3066088840736728
-0.3066088840736728 x 100 = -30.66%