-0.31% is the change from 638 to 636
Calculation steps:
[( 636 - 638 ) ÷ 638] x 100 = -0.31%
Formula
Percentage change = [(636 - 638) / 638] x 100
Subtract the new number by the original number
636 - 638 = -2
-2 ÷ 638 = -0.003134796238244514
-0.003134796238244514 x 100 = -0.31%