-97.25% is the change from 255 to 7
Calculation steps:
[( 7 - 255 ) ÷ 255] x 100 = -97.25%
Formula
Percentage change = [(7 - 255) / 255] x 100
Subtract the new number by the original number
7 - 255 = -248
-248 ÷ 255 = -0.9725490196078431
-0.9725490196078431 x 100 = -97.25%