Square footage refers to legal living area. In the city of Rochester, if an attic is finished living area, there must be a fire escape for egress. If there is no fire escape, the area would be unsafe to use as a living area. Sometimes people include finished basements in the square footage; however, if there is no means of egress, it is not legal living space. Also, if the basement is more than 1/4 underground, it is not generally included in the square footage. If you would like more information about this, I would recommend talking with the City of Rochester Assessor. The Assessor is VERY concerned about property square footage and legal living space!
I should mention that some realtors include space which is not legal living area. The tax records for properties are public documents which can help you verify actual square footage.
Good luck and I hope this was of some help.