My best understanding is that you need to file Form 843. The instructions for the form say that it can be used to request:

A refund or abatement of a penalty or addition to tax due to reasonable cause or other reason (other than erroneous written advice provided by the IRS) allowed under the law.

The "reasonable cause" here is a good-faith confusion about what Line 79 of the form was referring to.

In Form 843, the IRC Section Code you should enter is 6654 (estimated tax). For more, see the IRC Section 6654 (note, however, that if you already received a CP14 notice from the IRS, you should cross-check that this section code is listed on the notice under the part that covers the estimated tax penalty).

If your request is accepted, the IRS should issue you Notice 746, item 17 Penalty Removed:

We removed the penalty we charged you and we are reviewing your account. We will let you know the results

You can get more general information about the tax collection process, and how to challenge it, from the pages linked from Understanding your CP14 Notice.