How do you reveal a private number?

What does * 57 do on a phone?

It's a number of how many calls a person has in a month, and according to this chart I found it has a direct correlation to a person's income.

I find that the idea is interesting and the stats are quite surprising, but the data looks so raw that there's little to do with it. The chart looks like an attempt to compare the people's average spending on phone calls against their income. While I think that might be a bit of an interesting way to view it, I don't really see how that correlates to anything.