Yea, it should be NN.

This is an interesting idea. I like the way that you can keep track of the number of RCs you do. When people are starting out I suggest writing them down, but this way you don't have to carry something to write with, too. This sounds the same, good for people getting (back) into it.

Might be helpful to use a cut rubber band instead of a thread. Then if you find yourself knotting more than you anticipated, you can stretch it.