Karen,
I have no clue how that structure works. I do not know what the numbers mean.
Neither do most of us. 🙂 Every once in a while I want to investigate something (like, for instance, why my previews are currently not being produced... but that's another story), and I am reinvigorated to find things in the Aperture library package. That usually ends with me shrugging my shoulders and giving up...
When migrating from a PC to a Mac with Aperture, I had lots of heartache since I wanted everything to be transparent. Then I realized that Aperture isn't supposed to be transparent since it's a database. It just happens to use the file system to store things. Mac OS hides that from you (by making the library a package), but Carbonite just sees oodles of files.
However, I just wanted the transparency for the sake of it, and you are looking for a particular purpose. As Frank mentions below, using referenced masters will give you direct access only your masters, not the versions which you probably want. I suspect that, when you left home with your iPad, you did not know you wanted some pictures from Aperture. (If you had known that, you would have just synced your Aperture photos in iTunes and then you wouldn't need to ask this question, right? 🙂 )
I cannot think of a good way to maintain a collection of versions baked into JPGs. (That is to say, versions don't exist as full sized pictures within the Aperture library: they are only instructions to apply to a master, and then thumbnails for use within Aperture.) To gain those full sized pictures, you must export. Then you are using quite a bit more space on your hard drive, and you are backing stuff twice.
On top of that, Aperture will never overwrite files on export. That means that, if you have a project with 10 photos and export them all, but then add 5 photos, you cannot export them all again without having 25 files in your export directory -- 10 from the first batch, those 10 repeated again from the second batch, and then the difference. It would take quite a bit of effort on your part to export only the photos that were not in the first batch. (or else delete all files in the destination of your export and start from scratch.)
nathan