-10.31% is the change from 320 to 287
Calculation steps:
[( 287 - 320 ) ÷ 320] x 100 = -10.31%
Formula
Percentage change = [(287 - 320) / 320] x 100
Subtract the new number by the original number
287 - 320 = -33
-33 ÷ 320 = -0.103125
-0.103125 x 100 = -10.31%