KNN: How to caculate False Negative for a multiple Class problem?

Hi,
I was creating a model (having the classification class = 7). There were altogether 110 records, so taking a thumb rule for K as sqrt(110) i.e. 11, I did manage to achieve 83% accuracy. But I was more focused to get the FN (false negative) values to minimal.

Now, I need some help to clarify as in how the FN can be calculated altogether for a 7*7 matrix in R.

Thanks!

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