-36.81% is the change from 815 to 515
Calculation steps:
[( 515 - 815 ) ÷ 815] x 100 = -36.81%
Formula
Percentage change = [(515 - 815) / 815] x 100
Subtract the new number by the original number
515 - 815 = -300
-300 ÷ 815 = -0.36809815950920244
-0.36809815950920244 x 100 = -36.81%