Season 6 and 7 both have 2 parts which IMDb calls seasons 6/7 and 8/9, causing season 8 to be season 10 on IMDb, while Wikipedia and TVdb have 2 parts season 6 and 7 leading to the new season being 8.
This is the bane of my Plex organizing existence. Though luckily in this case Plex metadata and torrents agree on having 2 part season 6 and 7.