-20.72% is the change from 391 to 310
Calculation steps:
[( 310 - 391 ) ÷ 391] x 100 = -20.72%
Formula
Percentage change = [(310 - 391) / 391] x 100
Subtract the new number by the original number
310 - 391 = -81
-81 ÷ 391 = -0.2071611253196931
-0.2071611253196931 x 100 = -20.72%