Looking at the file, it strikes me that it doesn't seem to be quite what you think it is, namely a "relationship score" between Google+ users. People that I've never communicated with on Google+ but mailed previously have a score (and the people I've mailed most frequently have the highest scores), while people I've only communicated with on Google+ but never mailed don't have one (the fields are empty). Organizations that I've mailed also have scores, and they obviously don't have Google+ accounts.

It looks more like a "relationship score" for GMail that doesn't take into account Google+.