I'm assuming by "fake" named users, you just mean unlicensed user accounts.

If you have the license for 25 concurrent Public Portal connections, then the accounts themselves really don't matter; you're limit is just the number of simultaneous connections for unlicensed users.

Think of it like having 25 seats in a restaurant. It doesn't matter who, or how many, can get in, only 25 people will ever be able to sit down at the same time.

The accounts would really just be a way to limit who is allowed to enter in the first place; you can give access to as many as you want, but your seating is still limited.