"URL" (ranking url) column shows the actual indexed ranked URL.
It shows the URL that the Search Engine (Google for example) displays/links to for that tracked keyword, even if it's an inner page under the main domain that is tracked. It may differ from the URL you've entered if you have entered a main URL (example.com).
If the term Rank is NTH (Not Top Hundred), it will shows N/A in the URL column. It doesn't mean that it's not being tracked.
Once it will be in the top 100 results you will see the URL in this column.