Not sure if this is a known issue, but the Phyrexian Hydra tokens from March of the Machine (Extras #11 and 12) both seem to count themselves and each other in their own inventory count. I think the database simply has them flagged as variants of the same card (since they share a name), even though they're not.
All tokens with the same name behave this way. I have version numbers assigned to all tokens if you're ever interested in implementing this option, Sebi.