Zip Code (U.S.) or Postal Code...网申的时候这个填啥？

在填网申的表格...碰到了这么个东西。遂上网搜索答案...有的人回答说不用填，可是这个空是必填的。有的人说填00000，还有说查一个表的，广州是GD20...地里的大神们，这个Zip Code (U.S.) or Postal Code究竟该填什么呢？
P.s. 楼主的GRE分数一直查不到...注册过ETS那个GRE的账户了，所有信息都是从NEEA那边儿直接粘过来的，事后也double-check, triple-check过很多遍，信息是没有问题的。可是还是一查分就弹出来这个提示

Important Message[align="left"]The information you provided does not match our records. Please try again.[/align]

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想打电话给ETS，中国办事处能给解决吗？电话是这个010-82520176没错吧？