限る: to limit

この割引わりびきは今日きょうに限かぎります。

This discount is limited to today.

ただし、外国がいこくの人ひとが書かいた記録きろくなので、すべての人ひとが同おなじ服ふくを着きていたとは限かぎりません。

However, since this is a record written by foreigners, it does not mean that everyone wore the same clothes.