How to use Samba NAS add-on for Timemachine backup onto internal storage

I would like to use my HASS for Timemachine backup of my MAC book (running Sonoma).

I have a RPI4 with HassOS image 11.1 with 1TB M.2 SSD SATA disk (internal storage).
I did not define any additional partitions during the HASSOS installation, so default HassOS image install - it reports the 1TB of storage.

Running add-on Samba NAS 12.1.0-nas. I read the documentation and enabled the option “timemachine TRUE”. I can see the default shares and also see a “Timemachine” folder under the share called “share”. I have mounted the “share” but Timemachine report that it can’t see any useable storage.

From my mac I can add and delete files in the Timemachine folder so it does have r/w access to it.

Any ideas why TM won’t use/see the share?

Many thanks