-21.5% is the change from 642 to 504
Calculation steps:
[( 504 - 642 ) ÷ 642] x 100 = -21.5%
Formula
Percentage change = [(504 - 642) / 642] x 100
Subtract the new number by the original number
504 - 642 = -138
-138 ÷ 642 = -0.21495327102803738
-0.21495327102803738 x 100 = -21.5%