How to print how many nodes of a specific type a user has created?
The simplest way would be to extend the query from the other question you linked to and add the user id as an extra parameter:

function yourtheme_get_node_count($content_type) {
  $query = "
    SELECT COUNT(*) 
    FROM {node} n
    WHERE n.type = :type
    AND n.uid = :uid";

  // Get the node object for the current page.
  $node = menu_get_object();

  $params = array(':type' =&gt; $content_type, ':uid' =&gt; $node-&gt;uid);
  $amount = db_query($query, $params)-&gt;fetchField();

  return $amount;
}


Be sure to only call this on a node page as menu_get_object() will only return a node object when you're on such a page.