For user-based licensing, if not zero, overrides maximum sessions per user.
Most concurrent user licenses have a limit of 3 sessions per user by default.
If you have users that sometimes need more than 3 sessions, you can use this to enable a user to have more than the license.
Since there is still a maximum total session limit, note that if too many users exceed the limit you may run out of sessions if all users connect and need the amount of the license (for example, 3 sessions per user but one user has 5 sessions and all users are active).