Strange Interview Mishap

So this sort of strange thing happened regarding my admissions interview last week.

I became so absorbed in describing my experiences with an activity that I kind of “zoned out” from my surroundings, and only now realized that my interviewer was under the impression that I had done it for four years instead of three, and that I forgot to correct him.

If he writes that I did this activity for four years on my report, but on my application I say that I did it for three (correct), would this affect me negatively in any way?

No, I think you are thinking way too hard. They will be assessing your whole app, and won’t get caught up in this type of minutia on one EC. Don’t give it another thought.