The case received date is not the day the mail was delivered. It is the day that the case was input, created and a case number was assigned. One possibility for your case is that the package was delivered on 08/02 but you case was not input in their system until the H1b quota was reached.
One of my H1b cases was delivered to TSC on 09/08/2003 and the case was created on 09/16/2003, the expiry date of my previous H1b.
Good luck!