You'll find the details that Mentor releases in Ppcb_ASCII.pdf. Mine is located at "C:\Programs\Pads9.3\9.3PADS\docs\pdfdocs"; note that this isn't the normal installation directory.
This may vary with the version of PADS that you are using. In 9.3 I see the following defined on p. 55
If bit 4 is set, a diagonal hatch is generated; otherwise an orthogonal hatch is generated,
If bit 5 is set, vias are flooded over.
I don't see any detail for bit 6 (64) but you may find more info elsewhere in the document.