Favourite Series?

HI.
When I load Serviio (NAS based, various TVs) there is an option called "Favourite Series". Some things appear (like Marvel's Daredevil) and others don't (like Marvel's Iron Fist). I can't figure out why given that their individual folders are set up in the same way. Is there a setting in the Serviio console that controls what appears in Favourite Series?

Thanks in advance.
Bel

[zip]

It will include the last X series you have watched