Chrismast Events items

[zhuxianjian]

i'm the newbie here, today you guys 've just started Chrismast Event, that's cool but I just wonder it start today untill 24th December - 10 days but we have to "Collect at least 13 to exchange them for the best reward at Xmast Tree on 24th December"; so how could I get 3 more items for the best reward? =)))
Thanks alot and sorry for my bad English xD