I agree with ItsGavinC
The big numbers normally stand for Applicant I.D. #. This is an automatic number the applicant receives the minute they submit their application via web, or the minute AADSAS receives the application via mail and enter it in their records.
Mine was in the 7600's, and I sent it via web on Aug 28th. The same week AADSAS told me they processed 3500 application so far.
Thats around 4100 (7600-3500) applications not processed yet, with various reasons. It could be, 1500 have completed everything for the process and in the waiting line, 1500 of them havent submitted Letter of Recommendations, 1000 of them havent submitted their Transcripts, and 100 of them have not paid the processing fee. It could be any of the above combinations.
They do emphasize, that they process applications in order of receipt, this meaning that if your AADSAS I.D. was in the 6000's, and submitted everything, they will not process it before another applicant who's in the 5000's who also completed his/her application. However, if the person in the 5000's application has incomplete file, they wil process the individual in the 6000's who completed his/her application. This is just to make the process move forward.
I think, completing the application will always be the best bet, regardless what your AADSAS I.D. is. Don't let the big numbers scare you, you could get your application processed before someone who applied back in June, whose application is still incomplete.
Regards