It's not a big deal. The worst they will do is send a request for evidence for the Advance Parole, which you would send with a letter explaining that you forgot to check off the box. And the worksheet is mostly just supplemental to the application, your middle name doesn't determine your income and eligibility for employment authorization.

For all users on DAP, please double check your forms and make sure everything is in order. Mistakes can lead to denial of immigration benefits even if you qualify for them.