-17.74% is the change from 310 to 255
Calculation steps:
[( 255 - 310 ) ÷ 310] x 100 = -17.74%
Formula
Percentage change = [(255 - 310) / 310] x 100
Subtract the new number by the original number
255 - 310 = -55
-55 ÷ 310 = -0.1774193548387097
-0.1774193548387097 x 100 = -17.74%