Britsimon
Super Moderator
At your interview do not volunteer any unnecessary information. Don't say anything unless they specifically ask about it. If they ask about it come clean and be honest.
If you had made this mistake in your DV form that would be the end of the story for you. But fortunately you entered your DV forms correctly. A mistake in a prior visa application, if not intentional, may not come up at all or may be overlooked.
Excellent advice.