398.75% is the change from 80 to 399
Calculation steps:
[( 399 - 80 ) ÷ 80] x 100 = 398.75%
Formula
Percentage change = [(399 - 80) / 80] x 100
Subtract the new number by the original number
399 - 80 = 319
319 ÷ 80 = 3.9875
3.9875 x 100 = 398.75%
Example