-62.2% is the change from 820 to 310
Calculation steps:
[( 310 - 820 ) ÷ 820] x 100 = -62.2%
Formula
Percentage change = [(310 - 820) / 820] x 100
Subtract the new number by the original number
310 - 820 = -510
-510 ÷ 820 = -0.6219512195121951
-0.6219512195121951 x 100 = -62.2%