Are you already a selectee, or are you talking about the lottery just about to be announced?
Asssum you are DV2019, and I assume you mean the mix up was in the first entry. Presumably you corrected the error in the DS260. Correct?
If so, the reaction will vary by embassy, and by case. If your case is otherwise good with no other errors, and the embassy you apply at is not constantly seeing fraudulent cases, they will normally forgive the initial error. On the other hand, some cases get denied because there are other "problems" (incorrect birthdates and so on) which give concerns there was some attempt at multiple entries,