A lady and a man in a hat watch baseball from the stands.
Two people, one with a hat, can see baseball from where they are.
Two people a lady and a man watch baseball are in stands.
A lady and a man in a hat is used to describe the two people. The fact that they can see baseball from where they are implies that they are in the stands.
A lady and a man add up to be two people. Both are watching baseball from some location.