-8.93% is the change from 280 to 255
Calculation steps:
[( 255 - 280 ) ÷ 280] x 100 = -8.93%
Formula
Percentage change = [(255 - 280) / 280] x 100
Subtract the new number by the original number
255 - 280 = -25
-25 ÷ 280 = -0.08928571428571429
-0.08928571428571429 x 100 = -8.93%