It's not possible to achieve the desired result by using IMPORTXML alone, I think. Instead use Google Apps Script and the XML Service Service.

Example:

function parseFeedXml(url) {
   var result = [];
   var xml = UrlFetchApp.fetch(url).getContentText();
   var document = XmlService.parse(xml);
   var atom = XmlService.getNamespace('http://www.w3.org/2005/Atom');
   var feed = document.getRootElement();
   var entry = feed.getChildren('entry',atom);
   for (var i = 0; i < entry.length; i++) { 
     var content = entry[i].getChildren('content',atom);
     var contentElement = '';
     var resultRow = [];
     for (var j = 0; j < content.length; j++) { 
       contentElement = content[j];
       evaluateText(contentElement.getChild('filing-date',atom), resultRow);
       evaluateText(contentElement.getChild('filing-type',atom), resultRow);
       evaluateText(contentElement.getChild('filing-href',atom), resultRow);
       evaluateText(contentElement.getChild('form-name',atom), resultRow);
       evaluateText(contentElement.getChild('size',atom), resultRow);
       evaluateText(contentElement.getChild('amend',atom), resultRow);
       result.push(resultRow);                
     }
   }
   return result;
}

function evaluateText(element, resultRow) {
  if (element) {
    resultRow.push(element.getText());
  } else {
    resultRow.push('');
  }
}

Short answer

AFAIK, regarding XPath queries to be used with IMPORTXML there isn't straightforward method as XPath 1.0 support looks that was not fully implemented and the web pages developers could follow the practices to set the structure of their webpages.

Explanation

While the use of tools like Chrome Developer Tools or browser extensions/add-ons could be helpful sometimes these tools doesn't return a XPath query that could be used by IMPORTXML due to differences on how XPath support was implemented by the developers of each tool, by the other hand, web pages could comply or not with the XML rules, so to find the XPath query to be used with IMPORTXML could be necessary to analyze the structure of the source web page and to do several tries.

XPath queries for the use case

The below XPath queries returns 5,208.00

1.

//div[@id="balinterimdiv"]//tr[contains(.,'Total Debt')]/td[2]

2.

(//tr[contains(.,'Total Debt')]/td[2])[1]

Explanation

The referred page includes two views for the Balance Sheet: Quarterly Data and Annual Data. Both of them looks to have the same structure as both includes a table cell (td tag) with the text Total Debt. Fortunately, each view are inside a div tag and each of them have their own id, so in order to get only one, the first step in the XPath query could be to select the right view, then the second step could be to select the right table row (tr tag) and the third step to select the right table cell (td tag).

Another approach is to use the construct (xpath_query)[position() = 1] (see the reference).

References

• Answer by Dimitre Novatchev to What is the XPath expression to find only the first occurrence? referred by Dale in a comment to another answer to the question in this thread.