Notice: Undefined index: stored in ~/syndicatedlink.class.php on line 281

Same here. It’s just a standard PHP notice due to an uninitialized array value being incremented. Nothing to worry about (other than an error message on your page) but you can fix it like this:

if ( $new !== false ) {
  // RP - initialize array value to avoid PHP notice.
  if (!isset($new_count[$new])) {
    $new_count[$new] = 0;
  };
  $new_count[$new]++;
}