-40.35% is the change from 855 to 510
Calculation steps:
[( 510 - 855 ) ÷ 855] x 100 = -40.35%
Formula
Percentage change = [(510 - 855) / 855] x 100
Subtract the new number by the original number
510 - 855 = -345
-345 ÷ 855 = -0.40350877192982454
-0.40350877192982454 x 100 = -40.35%