Approval for 3rd floor

Probably this was something asked by many but just wanted to make sure that i get some right opinion on the issue i am facing, I am thinking about buying an apartment in Vidyaranyapura,. I have given all the property related documents to my lawyer for verification. He got back to me today saying that as per BBMP sanctioned plan what the builder has, only Ground + 2 floors approved. The property has parking space at the ground level and three floors above it + a pent house. I was planning to buy a 2BHK house in 3rd floor but as i understand it is not approved because BBMP has given approval only for G+2 floors. When i checked with builder he says that 1st floor is actually considered as ground floor and my apartment would be on the 2nd floor that way. I could really use some advice here, is it correct what builder says?