Not sure, their traffic stats page isn't super informative. It just has a breakdown of old reddit / new reddit / mobile web / official app. 3rd party apps are not counted.
Are these analytics coming from Reddit themselves? Call me paranoid, but I wouldn't be at all surprised to learn that they were massaging numbers to make it seem like fewer users were hitting old reddit.
They are coming from Reddit's own analytics. I do find it interesting how many more pageviews they see on mobile vs uniques?