-2.66% is the change from 638 to 621
Calculation steps:
[( 621 - 638 ) ÷ 638] x 100 = -2.66%
Formula
Percentage change = [(621 - 638) / 638] x 100
Subtract the new number by the original number
621 - 638 = -17
-17 ÷ 638 = -0.02664576802507837
-0.02664576802507837 x 100 = -2.66%