Hi Iebo,
When was your application processed? I checked with someone I know at a law firm, it seems that the actual letter of acknowledgement is dated the day the application was sent. E.g they had a client whose application was received on April 7, 2014, eCAS said the AOR and Discover Canada package was sent on April 7. However the letter of acknowledgement and book was received on July 22 and it was dated for June 5 which is the date their application was processed. Which is similar to the timeline with the person I know.
Hopes that help. Good luck