When you download the archive of personal data Facebook shares with you, it includes some facial recognition data. Specifically, it gives 3 "Threshold" decimal

When you download the archive of personal data Facebook shares with you, it includes some facial recognition data. Specifically, it gives 3 "Threshold" decimal values. Does anyone know what these numbers mean? I read up on "eigenfaces", and it sounds like Facebook is most likely subtracting my face from the mean and then projecting it onto N different face-like and orthogonal images to obtain numbers like this, and so these numbers would represent the weights used to reconstruct an approximation of my face from a linear combination of basis images. But N=3 is way too small for this method to be useful. It seems silly to share these values with a user but not tell them what it means.