Tweet text "default" prints "default"

'twitter' => array(
        'status' => 0,
        'dummy_img' => '',
        'txt_info' => '',
        'txt_twitter_off' => '',
        'txt_twitter_on' => '',
        'perma_option' => 0,
        'display_name' => '',
        'tweet_text' => 'default',
        'language' => 'system',
      ),

Prints "default [...] [URL]" in the tweet window. I now replaced 'default' by '' in this configuration and hope to fix it this way?
What's the true reason?