function getCountMessage () {
    switch (ctrl.matches.length) {
      case 0:
        return ctrl.noMatchMessage;
      case 1:
        return ctrl.singleMatchMessage;
      default:
        return ctrl.multipleMatchStartMessage + ctrl.matches.length + ctrl.multipleMatchEndMessage;
    }
  }
@returns {string} the ARIA message for how many results match the current query.