Fortunately this is not a very serious error, and is relatively easy to get corrected.
First of all, wait until you receive notice that USCIS has received your paperwork.
Then once you've received your Notice of Receipt, go ahead and call the National Customer Service Center, explain the mistake, and request that they fix it.
The phone number is *****(###) ###-####
They should be able to fix it right away. If for some reason they are not able to, then you can send in a written letter to the USCIS office that is processing your forms, explaining the mistake and how it should be corrected.
I hope that helps! Please let me know if you have any other questions. Also, please take a moment to rate me using the stars at the top of the page, as it's the only way experts are compensated for our time on the site. I do not receive a salary here at JustAnswer, and am only compensated for my time after receiving a rating of 3 stars or more.The question won't close after rating, so you can still ask follow-up questions after. Thanks, ***** ***** it!