Can someone tell me the expiry date of my multiple-entry China visa?

Just to confirm, I have a multiple entry visa that says enter befor sept 9 2011. Mo Problem, I will enter China on Sept 3. Also stated max stay is 30 days. No problem also, i am only staying for 7 days.
Concern is, I will leave China on Sept 10th, one day after the 'enter before' date.
I want to make sure 'enter before' date is not actually the expiry date or to confirm that expite date is really 30 days after 'enter before' date.