It's really on average 10% of what you need to lose. This is what we generally see most people lose although some will lose more and some will lose less.
How quickly you lose can also be influenced by a whole host of other things such as age, gender, past dieting history, medications and activity level.
For someone who started out at 200 lbs and wanted to get down to say 180, to lose the entire amount in 2 weeks would be very unusual.