can i be in china if my visa is not valid

Hi on my visa it is written that I should enter before 09 oct 2012 to china. The issue date of the visa was 09 jul 2012. The duration of each stay should be 12 days after entry. Does this mean i can enter china on the 8 oct and stay untill the 20 oct, or i am not allowed to stay after 09 oct because this is when the visa expieres?