-61.96% is the change from 815 to 310
Calculation steps:
[( 310 - 815 ) ÷ 815] x 100 = -61.96%
Formula
Percentage change = [(310 - 815) / 815] x 100
Subtract the new number by the original number
310 - 815 = -505
-505 ÷ 815 = -0.6196319018404908
-0.6196319018404908 x 100 = -61.96%