Chapter 10 Install and System Administration for FortiOS 5.0 : Basic Administration : Administrators
  
Administrators
By default, the FortiGate unit has a super administrator called “admin”. This user login cannot be deleted and always has ultimate access over the FortiGate unit. Additional administrators can be added for various functions, each with a unique username, password, and set of access privileges.
There are two levels of administrator accounts; regular administrators and system administrators. Regular administrators are administrators with any admin profile other than the default super_admin. System administrators are administrators that are assigned the super_admin profile, which has the highest level of access.
See Also
super_admin profile
Creating profiles
Management access
Adding administrators