We were also asked to upload our copy of the medical doc (the one they gave us to take home on the day of the test); the reason was that we had a hard time getting an appointment and were close to the end of the 30 day period. If you have undergone the test within 30 days, you should be fine - even if the clinic is later than that in submitting the final results. Still, the clinic wanted us to upload a pdf of the doc just as a guarantee.
We did so but, as it turned out, we didn't need it. The clinic submitted very quickly. But, I suppose in some cases, depending on the test results, it might take more time.
This is where we uploaded:
https://secure.cic.gc.ca/enquiries-renseignements/canada-case-cas-eng.aspx
I can't remember, but I think we picked 'Sponsorship' from the first dropdown, and went from there.