Here is the key information:
System-defined records are not editable or deletable.
How to add a record
You need to navigate to the Route (DNS) page.
Click Add Record.
In the Type option, select the desired type of record.
Specify the desired properties of that record.
Click Add.
Click Submit Group to save the zone.
How to modify a record
You need to navigate to the Route (DNS) page.
Click "Edit" next to the record that you would like to modify.
Modify record properties as needed.
Click Submit to save your changes.
Modifying the default set of system-defined records is not possible.
How to delete a record
You need to navigate to the Route (DNS) page.
Click "Delete" next to the record that you would like to delete.
Click Submit to save your changes.
It is not possible to delete the default set of system-defined records.