This transformation have been given a face lift in later releases, so I urge you to upgrade (either way)! If you look in the generated code you'll see the the table layouts, and even see the logic if you look to dig. The documentation here is quite scarce, but on short the error table contains the records that doesn't copy with the validation criteria (optional by defonition) and validation table tells you what actually went wrong. Its not uncommon you wish to joins those to get the full picture. Again, simpler and better in later releases.