If you are looking for specifically "6.1" content, it likely pertains to these releases:
The A Game of Thrones mod transforms the base game into the world of George R. R. Martin's A Song of Ice and Fire . Key features include: Agot Ck2 6.1
: A custom mechanic for handling large-scale civil wars. If you are looking for specifically "6
: Includes mechanics for dragons, White Walkers, Valyrian steel artifacts, and one-on-one duels. Valyrian steel artifacts
The content related to likely refers to historical versions of the popular A Game of Thrones total conversion mod for Crusader Kings II . While the mod eventually progressed to version 2.2 and beyond, version 0.6.1 and 1.6.1 were major milestones in its development. Core Mod Features