Grief, I really would be surprised for anyone new to running to run sub 5 mins for the mile......let alone 4:35, its borderline impossible!
There is only one way to find out if/or by how much the treadmill is flattering you........and its to get to your local running track and do a honest time trial. One mile is just a few metres longer than 4 laps of a standard 400m track (1,609 metres). I'd really like to hear how you do.
Two miles in just under 12 mins is a good intermediate time. Again, the treadmill might be flattering you. It is much, much less impressive than 4:35 for the mile though!