Control number of autocomplete results in drupal?
You will have to make a custom module to alter the result of autocomplete coming from node reference module. This example(taken from here) is for 20 result, you can increase/decrease according to your need. 

function MYMODULE_menu_alter(&amp;$menu) {
  if (isset($menu['nodereference/autocomplete'])) {
    $menu['nodereference/autocomplete']['page callback'] = 'MYMODULE_nodereference_autocomplete';
  }
}
function MYMODULE_nodereference_autocomplete($field_name, $string = '') {
  $fields = content_fields();
  $field = $fields[$field_name];
  $match = isset($field['widget']['autocomplete_match']) ? $field['widget']['autocomplete_match'] : 'contains';
  $matches = array();
  $references = _nodereference_potential_references($field, $string, $match, array(), 20);
  foreach ($references as $id =&gt; $row) {
    // Add a class wrapper for a few required CSS overrides.
    $matches[$row['title'] ." [nid:$id]"] = '&lt;div class="reference-autocomplete"&gt;'. $row['rendered'] . '&lt;/div&gt;';
  }
  drupal_json($matches);
}