-0.31% is the change from 320 to 319
Calculation steps:
[( 319 - 320 ) ÷ 320] x 100 = -0.31%
Formula
Percentage change = [(319 - 320) / 320] x 100
Subtract the new number by the original number
319 - 320 = -1
-1 ÷ 320 = -0.003125
-0.003125 x 100 = -0.31%