-0.31% is the change from 644 to 642
Calculation steps:
[( 642 - 644 ) ÷ 644] x 100 = -0.31%
Formula
Percentage change = [(642 - 644) / 644] x 100
Subtract the new number by the original number
642 - 644 = -2
-2 ÷ 644 = -0.003105590062111801
-0.003105590062111801 x 100 = -0.31%