I recently got 60 days late mark removed with Great Lakes also.  I was 60 days late then I decided to apply for a deferment and it was approved within a day, I then emailed customer service asking if they would kindly remove the late marks if I continue to keep the account in good standing. Then I got this reply below, I'm still don't understand the whole "backdating deferment" but I'm just happy that the late marks are finally gone from my report.

Thank you for your recent correspondence regarding the credit reporting of your Great Lakes student loan(s). 

Great Lakes Educational Loan Services Inc. is required by the Higher Education Act of 1965, as amended, to report the status on all serviced Title IV loans. The Fair Credit Reporting Act, as amended, requires that we report this information accurately and objectively. 

Our credit reporting process communicates monthly with Trans Union, Experian and Equifax. We began reporting your account on behalf of your lender at the time servicing began. Monthly reporting continues until your account is no longer serviced or is paid in full. 

In addition to reporting the status of the account, we are required to report delinquency data whenever warranted. Balances and amounts and dates of recent payments are also reported. Although the delinquency reported was correct, due to the backdating of your deferment, we have instructed all three Credit Reporting Agencies to remove the delinquency from January 2012.

This is no guaranty that correctly reported delinquencies can or will be removed in the future. Borrowers are responsible for all scheduled payments until they receive notice in writing that payments have been deferred or suspended. 

Please call us at 800-236-4300 with any questions regarding this information. Any of our Borrower Services Representatives will be happy to assist you. You can also view your account information on our website at www.mygreatlakes.org (http://www.mygreatlakes.org/)

Thank you.