Extra entry in the $node object

A dsm($node) shows these elements that appear to come from this module:

[field_link] => Array
        (
            [0] => Array
                (
                    [url] => www.example.com
                    [title] => 
                    [attributes] => N;
                    [view] => <a href="www.example.com">Website</a>
                )

        )

    [0] => Array
        (
            [url] => www.example.com
            [title] => 
            [attributes] => 
        )

What's the [0] entry? It doesn't look like it belongs there to me. Surely the $node object shouldn't have elements without proper names.