File 4 is $AttrDef, which contains the attribute names for all attributes used on the volume. Currently, only the well-known attributes should appear. Each definition has A0 bytes. At the beginning, the attribute name (Unicode) appears. It is not clear whether it is null terminated, or has a fixed size and is filled up with zeros. At offset 80 is the numerical value for the attribute. The purpose of any other data is not known. P. 32 gives some hints what else should be there.