$ umount /Volumes/UNTITLED
$ sudo ./wbfs -p /dev/disk4s1 init
$ sudo ./wbfs -p /dev/disk4s1 df
wbfs tot:298.08G used:0.08G free:298.00G
$ sudo ./wbfs -p /dev/disk4s1 ls
wbfs empty

Then just use WBFS for macos X to add in the backup images you've
created previously.