-40.8% is the change from 870 to 515
Calculation steps:
[( 515 - 870 ) ÷ 870] x 100 = -40.8%
Formula
Percentage change = [(515 - 870) / 870] x 100
Subtract the new number by the original number
515 - 870 = -355
-355 ÷ 870 = -0.40804597701149425
-0.40804597701149425 x 100 = -40.8%