Unable to delete local super admin user

Hello,

on my FortiGate I have two users as super-admin. Now I want to delete the one named "daniel" - but I cannot do this. There are no references in the GUI visible, and after searching via full-configuration on the CLI there is one entry. But I do not know how this settings came in the past to this, and also this is not visible in the GUI - or, at least, I did not see this yet. Anyway, I have no chance to get this entry changed so that the user is free to become deleted.

Please see attached screenshots. Any idea for this?

FortiGate 40F (FortiOS 7.6.3)

Regards,

Daniel