I have a feeling since it is integrated, that they are just listing how much ram it will take up from system ram, based on the ammount of system ram. I would take a guess that it would take more memory if you upgraded the ram to 2 gigs.
That's pretty good then, buy the "cheap" Mini and put in 4GB RAM from 3rd party, and you're golden. All you lack from the more expensive version is the 2.26 CPU then, which one could live without for that price