-2.81% is the change from 640 to 622
Calculation steps:
[( 622 - 640 ) ÷ 640] x 100 = -2.81%
Formula
Percentage change = [(622 - 640) / 640] x 100
Subtract the new number by the original number
622 - 640 = -18
-18 ÷ 640 = -0.028125
-0.028125 x 100 = -2.81%