The unknown folder seems to only have Work in Progress emails from GroupWise however these are NOT in any current Work in Progress folder.
A search in GroupWise will find the emails but it will say it's located in a 'find results' which cannot be found in any of the mail folders manually in GroupWise.
The emails appear to be older emails
Outlook Drafts should contain what was in Work in Progress but only seems to contain recent emails.
Run GWCheck against the mailbox several times and try the migration again.
Refer to Novell ArticleID:7003243 - "Successfully using GWCheck with the Deldupfolders option"