On Facebook chat list , I understand if there is a gray dot they are offline ..but?

[Mark]

If the person is offline , why are they on the chat list?

 

[•Angel•]

Try refreshing the page.
If someone is offline, They would not appear in the chat box, If someone logged off while chatting with you then their original green dot would turn gray.
If someone is online, they would have a green dot.

 

[soar]

It means they were online recently.