How I use the confidence variable to determine if a recognized face is not in our previously defined model?

Hello, I am using the following example:
https://github.com/justadudewhohacks/opencv4nodejs/blob/master/examples/faceRecognition1.js
After doing the recognition with the LBPHFaceRecognizert I could see that it returns a json, which contains the label and confience elements, the first one refers to the nameMappings and the second one I intuit referring to the percentage of similarity to the label. But my question is the following one exists the way to know if the identified face is not in our previously defined model.