How to know maximum final states in a DFA?
The set of final states in the DFA that results from the subset construction is given by

$$F' = \{ S \mid S \cap F \neq \emptyset\}$$

If there are $n$ states in $Q$ and $k$ final stages in $F$,
then there are $2^k-1$ nonempty subsets of $F$ and each of these can be occur together with a subset of the $n-k$ states that are not final.