My case status is in "Initial Review". I tracked my case with the receipt number, and this is what it says "On October 31, 2013, your Alien Registration Number was changed relating to your I765, APPLICATION FOR EMPLOYMENT AUTHORIZATION. Please check our website at www.uscis.gov for further updates on your case. Please wait until the end of normal processing time before calling customer service at 1-800-375-5283 for live assistance."
It is common. No worries.
This answer is for informational purposes only and should not be construed as legal advice.
Don't waste time trying to find out ... it is normal for them to do this to F-1 OPT EAD applicants.
If you apply for a greencard .. .they'll change it again ... it is no big deal.
PROFESSOR OF IMMIGRATION LAW for over 10 years -- This blog posting is offered for informational purposes only. It does not constitute an attorney-client relationship. Also, keep in mind that this is an INTERNET BLOG. You should not rely on anything you read here to make decisions which impact on your life. Meet with an attorney, via Skype, or in person, to obtain competent personal and professional guidance.