The IMDB listing is meaningless.  There are too many possible reasons that it appears as it does.  

Mentalist creator/writer Bruno Heller says that Red John is on Jane's list, http://insidetv.ew.com/2013/05/06/mentalist-finale-season-6-red-john-list/
The list does not include Mashburn.  But...

It is likely that Red John has become a title that is passed on to the leader each generation.  So...a current or former Red John is on Jane's list, but not necessarily both.  Mashburn is a possible Red John, but very unlikely, even with what IMDB says. 

The Red John dynasty has it's roots with the Visualize church, and a strong connection to the Tyger-Tyger organization.  One model that explains this has Stiles as founder and his son Reede Smith as the current Red John. Reede Smith brings many police officers into the Visualize church and builds a very influential organization.  Red John is now an organizational serial killer.  Those who are killed are often people who simply know too much...about Red John, or Tyger-Tyger or about a member.  

Red John did get into Jane's mind and plant the list.  He did it when he knocked out Jane and held him hostage for a day.  Red John is the master of mind manipulation, and he learned it at Visualize.