现在有四种合约，Contract1, 2, 3, 4，然后我最后的一句不明白什么意思了。


For crude oil, each contract expires on the third business day prior to the 25th calendar day of the month preceding the delivery month. If the 25th calendar day of the month is a non-business day, trading ceases on the third business day prior to the business day preceding the 25th calendar day. After a contract expires, Contract 1 for the remainder of that calendar month is the second following month.

在合约过期后，剩下的日历月中.......


应该怎解释呀？