-4.49% is the change from 668 to 638
Calculation steps:
[( 638 - 668 ) ÷ 668] x 100 = -4.49%
Formula
Percentage change = [(638 - 668) / 668] x 100
Subtract the new number by the original number
638 - 668 = -30
-30 ÷ 668 = -0.04491017964071856
-0.04491017964071856 x 100 = -4.49%