-61.35% is the change from 815 to 315
Calculation steps:
[( 315 - 815 ) ÷ 815] x 100 = -61.35%
Formula
Percentage change = [(315 - 815) / 815] x 100
Subtract the new number by the original number
315 - 815 = -500
-500 ÷ 815 = -0.6134969325153374
-0.6134969325153374 x 100 = -61.35%