To configure administration for local groups
Enable Number of concurrent sessions and enter the maximum number of users who can log in simultaneously without needing to log out and back in.
To do a mix of both, select the first option for SonicWall Read-Only Admins, and then create another group that is a member of this group, but that has the second option selected (but not vice versa).
If a user is a member of a read-only admin group and has membership in no other administrative groups, then that member gets full-level access (as per SonicWall Administrators) restricted to read-only.