-15.83% is the change from 815 to 686
Calculation steps:
[( 686 - 815 ) ÷ 815] x 100 = -15.83%
Formula
Percentage change = [(686 - 815) / 815] x 100
Subtract the new number by the original number
686 - 815 = -129
-129 ÷ 815 = -0.15828220858895706
-0.15828220858895706 x 100 = -15.83%