-84.71% is the change from 255 to 39
Calculation steps:
[( 39 - 255 ) ÷ 255] x 100 = -84.71%
Formula
Percentage change = [(39 - 255) / 255] x 100
Subtract the new number by the original number
39 - 255 = -216
-216 ÷ 255 = -0.8470588235294118
-0.8470588235294118 x 100 = -84.71%