When running a Deletion Management job and the Profile is set to find all mail that has an expiration date older than (x) amount of days, the CSV report will show that there is mail with an expiration date in the future showing on the list
This only happens when the Indexes and the Database do not match their records. The only solution would be to reindex everything so that the indexes are referring to the correct expiration date. Depending on size of indexes and thread speeds, this can take days or weeks to complete.
There are 2 possible causes to this issue. Either the expiration date was manually changed in the database (which won't work because that will not change the expiration date in the indexes) or the indexes were corrupted at some point. In either case, the resolution of reindexing is the only way to correct to the problem.