-0.9% is the change from 670 to 664
Calculation steps:
[( 664 - 670 ) ÷ 670] x 100 = -0.9%
Formula
Percentage change = [(664 - 670) / 670] x 100
Subtract the new number by the original number
664 - 670 = -6
-6 ÷ 670 = -0.008955223880597015
-0.008955223880597015 x 100 = -0.9%