>...According to the CONTENTS table, the AGGREGATED
>value for this file is 34/65 and the filesize is 42153627 bytes.)

In that table, the FILE_SIZE column is an historic name.  As of ADSMv3
it really records Aggregate size, so take that into account.  Large files
may exceed the Aggregate size, and so may reflect actual file size.
If this were easy, we'd all be paid a lot less.

   Richard Sims, BU