刚收到E-MAIL：
Application Type: I485, APPLICATION TO REGISTER PERMANENT RESIDENCE OR TO ADJUST STATUS
Current Status: Document mailed to applicant.
On March 28, 2008 we mailed the document to the address we have on file. You should receive the new document within 30 days. If you do not, or if you move before you get it, call customer service.
这是什么document? 我看到以前有人也收到过这种E-MAIL.但没有人说是什么。 有人了解吗？多谢！
另外多长时间能收到？ 再谢！