-6.18% is the change from 680 to 638
Calculation steps:
[( 638 - 680 ) ÷ 680] x 100 = -6.18%
Formula
Percentage change = [(638 - 680) / 680] x 100
Subtract the new number by the original number
638 - 680 = -42
-42 ÷ 680 = -0.061764705882352944
-0.061764705882352944 x 100 = -6.18%