short sale problem need help, please

lender gave us a apprvol letter for a short sale, but just found out they amended some term from my offering letter, is this a counteroffer or I am already bingding to an official contract? my agent said even the bank did not 100% agree my offer, we still offically in contract, is this right? and on the approval letter the lender did not mention on which part they has rejected, they just said they aproval the price, how can we get more detail, Thank you very much for your help.