-19.91% is the change from 638 to 511
Calculation steps:
[( 511 - 638 ) ÷ 638] x 100 = -19.91%
Formula
Percentage change = [(511 - 638) / 638] x 100
Subtract the new number by the original number
511 - 638 = -127
-127 ÷ 638 = -0.19905956112852666
-0.19905956112852666 x 100 = -19.91%