-2.75% is the change from 255 to 248
Calculation steps:
[( 248 - 255 ) ÷ 255] x 100 = -2.75%
Formula
Percentage change = [(248 - 255) / 255] x 100
Subtract the new number by the original number
248 - 255 = -7
-7 ÷ 255 = -0.027450980392156862
-0.027450980392156862 x 100 = -2.75%