I have no idea if it is the same in Shanghai, but in my city, it takes 5 working days for the paperwork turned in to you pick up passport with the extension. They make it clear that you should apply no less than 5 days prior to expiration date.

Now, here they also tell you when to return to their office to pick up your passport, and give you a paper or receipt to claim it with. Did they tell you that ?

They asked me if I want it sent to my home or pick up. I chose to let them send it.