You always get duplicates in TOSEC sets. Look through your Amiga ones and I'm sure you will find a lot too. The [b] info flag in your example duplicate file means a bad dump. These files often still work fine, but are flagged by TOSEC convention as a bad dump due to a read error in a sector or track. Including them just makes the full known set, as the original version it was taken from might have had this error across the whole release, and not just the disk dumped from. It depends how much you want a complete TOSEC set in your collection though, as you could in theory delete all these bad dump versions and just keep the good versions and the alternate versions [a]. Obviously updating a torrent would be an issue then though.