不清楚national express的票價差異 - 留學

搞胡塗了...
我定的票,最便宜的那種顯示
Valid on off-peak services by the route and Train Operator shown.
Return journey must be made the same day.
第二便宜的那種顯示
Valid outward and return by the route and Train Operator shown, return same
day.

這是甚麼意思啊?可以請知道的先進解答一下嗎? 很怕坐錯車多罰冤枉錢.

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