-7% is the change from 686 to 638
Calculation steps:
[( 638 - 686 ) ÷ 686] x 100 = -7%
Formula
Percentage change = [(638 - 686) / 686] x 100
Subtract the new number by the original number
638 - 686 = -48
-48 ÷ 686 = -0.06997084548104957
-0.06997084548104957 x 100 = -7%