-49.1% is the change from 501 to 255
Calculation steps:
[( 255 - 501 ) ÷ 501] x 100 = -49.1%
Formula
Percentage change = [(255 - 501) / 501] x 100
Subtract the new number by the original number
255 - 501 = -246
-246 ÷ 501 = -0.49101796407185627
-0.49101796407185627 x 100 = -49.1%