Update information on mkdocs build process

docs/builds.rst

@@ -46,7 +46,12 @@ we will first look for a ``mkdocs.yml`` file in the root of your repository.
 If we don't find one,
 we will generate one for you.
 
-Then MkDocs will build any files with a ``.md`` extension.
+Then MkDocs will build any files with a ``.md`` extension within the directory specifed as ``docs_dir`` in the ``mkdocs.yml``. 
+
+If no ``mkdocs.yml`` was found in the root of your repository and we generated one for you, 
+Read the Docs will attempt to set ``docs_dir`` by sequentially searching for a  ``docs``, ``doc``, ``Doc``, or ``book`` directory. 
+The first of these directories that exists and contains files with a ``.md`` extension will be set to ``docs_dir`` within ``mkdocs.yml``,
+and MkDocs will build the ``.md`` files in that directory. 
 As MkDocs doesn't support automatic PDF generation, 
 Read the Docs cannot create a PDF version of your documentation with the *Mkdocs* option.