You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <allcategories accontinue="Wikipedia_pages_with_incorrect_protection_templates" />
  </query-continue>
  <query>
    <allcategories>
      <c size="0" pages="0" files="0" subcats="0" xml:space="preserve">%s</c>
      <c size="0" pages="0" files="0" subcats="0" xml:space="preserve">' .. cat .. '</c>
      <c size="0" pages="0" files="0" subcats="0" xml:space="preserve">All pages needing cleanup</c>
      <c size="82" pages="82" files="0" subcats="0" xml:space="preserve">Atlas Release Notes</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">Documentation shared content templates</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">Hatnote templates documentation</c>
      <c size="0" pages="0" files="0" subcats="0" xml:space="preserve">Hatnote templates for user pages</c>
      <c size="0" pages="0" files="0" subcats="0" xml:space="preserve">Pages with broken file links</c>
      <c size="0" pages="0" files="0" subcats="0" xml:space="preserve">Roman Catholicism templates</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">TemplateData documentation</c>
    </allcategories>
  </query>
</api>