-50.31% is the change from 642 to 319
Calculation steps:
[( 319 - 642 ) ÷ 642] x 100 = -50.31%
Formula
Percentage change = [(319 - 642) / 642] x 100
Subtract the new number by the original number
319 - 642 = -323
-323 ÷ 642 = -0.5031152647975078
-0.5031152647975078 x 100 = -50.31%