99.5% is the change from 401 to 800
Calculation steps:
[( 800 - 401 ) ÷ 401] x 100 = 99.5%
Formula
Percentage change = [(800 - 401) / 401] x 100
Subtract the new number by the original number
800 - 401 = 399
399 ÷ 401 = 0.9950124688279302
0.9950124688279302 x 100 = 99.5%