Help understanding logistic model equations

https://www.khanacademy.org/math/integral-calculus/ic-diff-eq/ic-logistic-models/v/logistic-function-application

at 4:53,

1.5^(1/20) tells you 1.02048015365. However, Khan said 1.02048.

what reasons the number, 1.02048, gives you that is a significant figure?

I couldn't get it.

and also, Annual growth, A=0.0205,

is the result came from formula, =(Last Value/First Value)^(1/Period)-1?