-9.22% is the change from 640 to 581
Calculation steps:
[( 581 - 640 ) ÷ 640] x 100 = -9.22%
Formula
Percentage change = [(581 - 640) / 640] x 100
Subtract the new number by the original number
581 - 640 = -59
-59 ÷ 640 = -0.0921875
-0.0921875 x 100 = -9.22%