-1.08% is the change from 647 to 640
Calculation steps:
[( 640 - 647 ) ÷ 647] x 100 = -1.08%
Formula
Percentage change = [(640 - 647) / 647] x 100
Subtract the new number by the original number
640 - 647 = -7
-7 ÷ 647 = -0.010819165378670788
-0.010819165378670788 x 100 = -1.08%