-17.69% is the change from 390 to 321
Calculation steps:
[( 321 - 390 ) ÷ 390] x 100 = -17.69%
Formula
Percentage change = [(321 - 390) / 390] x 100
Subtract the new number by the original number
321 - 390 = -69
-69 ÷ 390 = -0.17692307692307693
-0.17692307692307693 x 100 = -17.69%