My case in NSC

Oct 2003 file 140 and 485 in the same time, EB2, May 2004 FP, but yesterday I got a message from website, say" On December 28, 2004, we mailed a notice requesting additional evidence or information in this case. The notice explains in detail what additional material is needed. If you have questions about the notice, what is required, or if 14 days have passed and you have not received the notice, please call the National Customer Service Center at [phone], I am nervous, what it could be?