The limit you hit is the limit of the objects actually rendered, so anything outside camera frustum does not count.
I can't tell off the top of my head, if objects are getting culled if the cell they're in are not rendered (like behind the wall or behind the closed door), but I believe they do not count.
You can get exact information on the object rendered on screen using show_stats command. (note, it has two modes - short and full (or something like that), so make sure you get the full stats. It's in the 8th line here - Visible objects: