When you want to file an infringement notice pursuant to the DMCA, you determine where to send that notice by looking up the service provider's agent at the list on the copyright office website. That's what these filings are for, adding your company's agent to the list, so copyright holders know how to reach you. The notices are sent to the designated agent, not to the copyright office.

http://www.copyright.gov/onlinesp/list/a_agents.html