-21% is the change from 643 to 508
Calculation steps:
[( 508 - 643 ) ÷ 643] x 100 = -21%
Formula
Percentage change = [(508 - 643) / 643] x 100
Subtract the new number by the original number
508 - 643 = -135
-135 ÷ 643 = -0.2099533437013997
-0.2099533437013997 x 100 = -21%