Thanks for the response.
I saw this information as well. I thought the sys_userid was set. It seems to be set by who is currently logged in
There seem to ebe a misunderstanding on what the sys_userid is. the sys_userid is a internal ID used by ispconfig to configure the permissions for records in the database. The sys_userid is the ID of the user that is currently logged into the ispconfig interface (or when the admin created it, then its the userid of the sys_user that is associated with the client that shall own a record) which has created that specific record. So the sys_userid is always the same for all mailboxes of a given domain in ISPConfig.
That the sys_userid is identical with the sys_groupid in your example is just a coincident.