30.58% is the change from 399 to 521
Calculation steps:
[( 521 - 399 ) ÷ 399] x 100 = 30.58%
Formula
Percentage change = [(521 - 399) / 399] x 100
Subtract the new number by the original number
521 - 399 = 122
122 ÷ 399 = 0.3057644110275689
0.3057644110275689 x 100 = 30.58%