This is a "rounding problem". The population size after 6 years is P(6):
[tex]P(6)=\frac{450}{1+8\cdot e^{-0.29\cdot(6)}}\approx187.175[/tex]
Now, for the first decimal place (1) is less than 5, 187.175 becomes 187 (by the rounding rule); namely,
[tex]P(6)\approx187[/tex]
On the other hand, the population size after 8 years is P(8):
[tex]P(8)=\frac{450}{1+8\cdot e^{-0.29\cdot(8)}}\approx251.93[/tex]
Now, for the first decimal place (9) is greater than 5, 251.93 becomes 252; namely,
[tex]P(8)\approx252[/tex]
