-4.34% is the change from 668 to 639
Calculation steps:
[( 639 - 668 ) ÷ 668] x 100 = -4.34%
Formula
Percentage change = [(639 - 668) / 668] x 100
Subtract the new number by the original number
639 - 668 = -29
-29 ÷ 668 = -0.04341317365269461
-0.04341317365269461 x 100 = -4.34%