Most agents get the info for living area from public records. I would ask your agent if this is where they got their figure from. The discrepency may be due to an addition that was never recorded. To change the public record you would probably need to contact your tax assesors office & let them know. You may want to take your own measurements so that you can give that info to your agent, who in turn can change the listing to reflect the true size of your home.