Duration of China tourist visa.

hi we are mohammad bannout and malik el tawil from lebanon , we are right now in china (xian) , we have reached china on June 29 . we will stay in china about 2 months , but we have noticed yesterday that it's registered on our visas just 30 days in the case of duration of stay , even though that the chinese embassy knows from the invitation to china and the booking of our tickets that we will stay in china for 2 months and we have paid for this duration .what we are supposed to do now??? thank you