A group of people sitting around a table eating food.
A person eats a tv dinner while sitting on the couch.
It is either a person or a group of people, and the person/group is either sitting at a table or sitting on the couch, but not both.
A person is not a group of people.  If people are sitting around a table they are not sitting on the couch.
There cannot be a group of people and one person at the same time. A person cannot sit around a table while sitting on the couch.