The number inside console log after the Exit button is clicked represents what?

After clicking on the exit buttons, one at a time,

If I see it do this, what does that tell mean?

If the numbers go: 1, 3, 6, 10

What is it telling me?

As is the case here: https://jsfiddle.net/o2zn7309/

It goes from 1, to 3, to 6, to 10

What does that mean? @snowmonkey