There are several possibilities; the home may have been a 2/2 when originally built but had another bedroom added on. The Home may have had an open loft or other section of the house converted to a legal bedroom. The public record may not reflect changes done by the owner but the listing would.
To be a true legal bedroom a room must have a window large enough to escape through and a closet. On occasion an agent or owner will refer to a den/office as a bedroom that may not be considered a legal bedroom.
I can't see what home you are asking about, you can inquire with any local agent who can research this for you.