Hi Edith I-H,
it's good to hear that you've been using the system successfully and welcome to the group!
If you've installed it using the rpms or if you've downloaded the appliance, you'll have a GUI user called "sdmsadm" and if you didn't change the password, that'll be "sdmsadm" as well.
If you've installed from the sources, following the installation instructions, this is likely to be true too.
I'll explain this a little.
You can define multiple "connections" per GUI user.
One reason to do this could be because you have a Dev, Test and Prod schedulix server running.
Another reason could be that you'd like to work with a less privileged schedulix user per default, but need privileged access every now and then.
(Both reasons are true in my environment here).
If you've been working with a tool like PuTTY or sqlworkbench, you've seen that concept before.
In order be allowed to use those "connections" you'll have to authenticate with the Zope Server.
The Zope server does not know anything about a user SYSTEM, but knows its management user sdmsadm.
This can be changed, of course.