Here are some possibilities:
* A specific organization or unit: It could be a designation for a particular group or team, like a K-9 unit but focused on a different area.
* A fictional element: It might be a term used in a book, movie, or game.
* A code or abbreviation: It could stand for something specific in a certain field, like military or aviation.
Without more information, it's impossible to say for sure what "K-6" refers to.