-19.22% is the change from 640 to 517
Calculation steps:
[( 517 - 640 ) ÷ 640] x 100 = -19.22%
Formula
Percentage change = [(517 - 640) / 640] x 100
Subtract the new number by the original number
517 - 640 = -123
-123 ÷ 640 = -0.1921875
-0.1921875 x 100 = -19.22%