Hi there!
I found this article to be interesting, and is geared towards guys. I think the bottom line is that it takes a LONG time for a person to increase their muscle mass. The guy in the article says that a man with perfect training, eating, and supplementation can gain 0.25-0.5 lbs of dry muscle weight a week, or 1-2 lbs per month. BUT you also add glycogen and fat to that (if your purpose if muscle building, as a result of increased caloric intake).
http://www.ironmagazine.com/viewarticle-3995.html
So assuming that you are a woman, 1/2 lb in one month is pretty much bang on, because women don't gain muscle as quickly.
But, like Nelie says, there are SO many factors (body composition, body type, hormonal makeup, diet, supplementation, workout schedule, workout routine, intensity, and so on) that this answer is not definitive...
Congrats, though, on the 7 lbs loss and the 1/2 lb muscle gain!
Kira