When you enable the Trailing Stop option in your operation, all open orders will have this message "Undefined" in the sales field, because the Trailing Stop has not yet been activated and as this tool does not work with a fixed gain value, this value it will be relative.

After the Trailing Stop is triggered in its order, the message Undefined will be hidden and a new value will appear in this field, with a blue arrow indicating that the Trailing Stop is activated.