The postal address is the default from the ATO prefill.
When an AS is created via the Prefill, then most information, like the address, is read-only as the information is being generated as per the ATO portal
You can contact ATO and update the details, or update the details via the ATO portal
Note: When the Activity statement is prefilled, the Integrity check will not update the address. However, when an AS is created as blank, then the user can peruse the information from Practice Management. Return Integrity check will update the address to whatever changes occurred.