3 pounds in 6 six days is TREMENDOUS progress no matter what diet/exercise you are doing.
I am not saying this to keep you optimistic on a bad day or whatever. I am saying this because it truly is a fast clip.
Most weight loss is slower especially at your current weight.
Where are you seeing these bigger losses? Are they on heavier folks than yourself or adverts on the SB website? Both of which are not applicable to you.
BTW I don't adhere to South Beach Diet but I am familiar with it. Just saw the post on New Posts and thought... do you REALLY not know how good that it?
Anything faster would be getting into the unrealistic range.