-20.72% is the change from 642 to 509
Calculation steps:
[( 509 - 642 ) ÷ 642] x 100 = -20.72%
Formula
Percentage change = [(509 - 642) / 642] x 100
Subtract the new number by the original number
509 - 642 = -133
-133 ÷ 642 = -0.2071651090342679
-0.2071651090342679 x 100 = -20.72%