Not the RAM, but the flash memory. The naming "Available Memory" was taken right from iOS own settings. And of course I only have 1.1 GB free once all my apps are installed.
After updating to iOS 9 the 1.1 GB turned into 0.55 GB (give or take a little depending on what the iPad is busy with). I looked at the free space counter right before hitting the Update button. So iOS 9 (ab)uses over 500 MB of additional space. Too bad, because I hoped for v9 to be more efficient than 8, not less.
I couldn't care less for my 128 GB iPad mini 2, or even our 32 GB iPhone. But the 16 GB units really suffer from this kind of bloat, especially since Apple still has the audacity to sell so little flash space for its base models.