-7.27% is the change from 688 to 638
Calculation steps:
[( 638 - 688 ) ÷ 688] x 100 = -7.27%
Formula
Percentage change = [(638 - 688) / 688] x 100
Subtract the new number by the original number
638 - 688 = -50
-50 ÷ 688 = -0.07267441860465117
-0.07267441860465117 x 100 = -7.27%