-8.5% is the change from 306 to 280
Calculation steps:
[( 280 - 306 ) ÷ 306] x 100 = -8.5%
Formula
Percentage change = [(280 - 306) / 306] x 100
Subtract the new number by the original number
280 - 306 = -26
-26 ÷ 306 = -0.08496732026143791
-0.08496732026143791 x 100 = -8.5%