If the heading numbering has been switched on via via 

This property also works on document level by the same name. If set on a document, only the title of the given document will be provided with a heading number.

The projectdoc Toolbox will add styles for the CSS to render the heading. This works with standard Confluence using the selector h1#title-text:before. If you are using additional tools for layout, you may need to adjust your configuration accordingly.