-39.95% is the change from 866 to 520
Calculation steps:
[( 520 - 866 ) ÷ 866] x 100 = -39.95%
Formula
Percentage change = [(520 - 866) / 866] x 100
Subtract the new number by the original number
520 - 866 = -346
-346 ÷ 866 = -0.3995381062355658
-0.3995381062355658 x 100 = -39.95%