-68.71% is the change from 815 to 255
Calculation steps:
[( 255 - 815 ) ÷ 815] x 100 = -68.71%
Formula
Percentage change = [(255 - 815) / 815] x 100
Subtract the new number by the original number
255 - 815 = -560
-560 ÷ 815 = -0.6871165644171779
-0.6871165644171779 x 100 = -68.71%