-63.53% is the change from 850 to 310
Calculation steps:
[( 310 - 850 ) ÷ 850] x 100 = -63.53%
Formula
Percentage change = [(310 - 850) / 850] x 100
Subtract the new number by the original number
310 - 850 = -540
-540 ÷ 850 = -0.6352941176470588
-0.6352941176470588 x 100 = -63.53%