The purpose of AOR (Acknowledgment of Receipt) is just that CIC has received your application and will review further. An application number (important one) is given. The best part here is that your application is not returned back. SO just relax and just wait, the journey to citizenship has...
Also, can you please share some details so the tracking sheet can be updated:
Location, How many applications (single, family?), Physical presence days, application received date?