Hi Michael,
Written DB space in MB = Written (DB Table Space in MB + DB Index Space in MB + Cluster Space in DB)
With same logic, Deleted DB Space in MB = Deleted DB Table Space in MB + Deleted DB Index Space in MB.
Most of the time the archived data (including all DB links and indexes) can be removed after the archiving has been completed successfully but in some cases it is not possible to remove all related DB indexes and links due to the dependencies with other objects / tables.
Because the main target of data archiving is to increase DB performance (not cleaning up some DB space), it's better to analyse and focus on the performance improvement rather than the space cleaned up.
Kind regards,
Alper