-0.32% is the change from 310 to 309
Calculation steps:
[( 309 - 310 ) ÷ 310] x 100 = -0.32%
Formula
Percentage change = [(309 - 310) / 310] x 100
Subtract the new number by the original number
309 - 310 = -1
-1 ÷ 310 = -0.0032258064516129032
-0.0032258064516129032 x 100 = -0.32%