It means that the movie equals to the chapter 699,5, meaning that the story of The Last is placed between 699 and 700. That's to say if The Last was a chapter and not a movie it would be 699,5. LOL Was I clear (I think I wasn't)?
In other words it's completely canon and more canon than RTN.... lol... wow.
But this is a poster or an ad or a cover to something?