They're checking on the genuineness of your application based on your supporting documents, i guess.

I've heard from some applicants who attended the same seminar i have been before i lodged my appl for a visa....
these questions:
>One student asked why the long wait, she presented docs like receipts (of her tuition fees, uniforms, accomodation etc).
>Another student said she has presented a fat passbook and the date of the classes indicated.

Just be patient hope you will get your visa soon. AS long as your docs are genuine and complete.

Best of luck..