I just had a look on the frequent questions of such ticket on the saler's page.
1. this type of the ticket is only for 有打折卡的人,有火车月票年票的人 (een geldig NS abonnement heeft.)( to prove you are entitled for this, you should have abonnement 卡 with you
2。this type of the ticket only can be used 工作日9 点以后, 周末和12 月25- 1月1日期间的全天3。 售票日期 15 december 2009 tot en met 3 januari 2010
使用期限 28 februari 2010