-36.07% is the change from 815 to 521
Calculation steps:
[( 521 - 815 ) ÷ 815] x 100 = -36.07%
Formula
Percentage change = [(521 - 815) / 815] x 100
Subtract the new number by the original number
521 - 815 = -294
-294 ÷ 815 = -0.36073619631901843
-0.36073619631901843 x 100 = -36.07%