Undevided property

I need some help please to solve this case:

One survey number two owners A & B

A=  Agreement deed  documents  & 7/12 reflect size of the property 1000 SqFt,  but property card has 500 spft the actual size of the room.

B= Construction plans submitted  using A's  unclaimed area that mean 500 SqFt from  A

I appreciate your valuable time and advice.

Thanks Best Regards

S Patel