H1B is valid for more than 6 years, 7th year ext ???

[balag]

I got my first H-1B starting from 09/2000. I applied for ext. and my H-1B was extended in 2004. Somehow my H-1B expiration date on this extension was 07/2007 instead of 09/2006 by the BCIS mistake as this was exceeding my 6 year H1B visa limit

Now I am planning to apply for 7th year extension based on my LC filing. What should I do to make them understand about my problem