/**
 * Implements hook_block_configure().
 */
function {{ machine_name }}_block_configure($delta = '') {
  // This example comes from node.module.
  $form = array();
  if ($delta == 'recent') {
    $form['node_recent_block_count'] = array(
      '#type' => 'select',
      '#title' => t('Number of recent content items to display'),
      '#default_value' => variable_get('node_recent_block_count', 10),
      '#options' => drupal_map_assoc(array(2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30)),
    );
  }
  return $form;
}