When you download your Facebook data, you get this
MyReal RealName Facial Recognition Data Threshold 1 3.2382398572935 Threshold 2 3.0234235928592 Threshold 3 1.7239528352435 Example Count 120
What do these numbers mean?
Example count is the number of pictures of you that Facebook has.
Threshold values and
Raw Data are produced by machine learning, and any picture of you should generate similar numbers. This data helps Facebook guess whether a picture shows your face or not.
Rather than storing individual measures such as "proportion of nose", machine learning store such values that have no easily understandable meaning to humans:
So what parts of the face are these [...] numbers measuring exactly? It turns out that we have no idea. It doesn’t really matter to us. All that we care is that the network generates nearly the same numbers when looking at two different pictures of the same person.