when should I make a service request on I-485 pending case? ninohu2008-08-13 18:22:00

Hi, Need your suggestion:

My case: EB2 PD was 8/2004. I-140 approved last July. i-485 filed on 7/2/2007.

I called USCIS yesterday and they told me to make a service request after 16 days. I asked 3 times to figure out why I have to wait 16 days but still did not understand.

Please let me know when should I call to make a service request and what should I request?

Thanks