I never heard that number, but whoever came up with it, it's a statistical probability based on the facts we know, and it's possible there are facts we don't know.
If there are other inhabited planets in our galaxy, the nearest one would be at least dozens of light years away, more likely hundreds of light years. Meaning we couldn't communicate with them, as a practical thing, much less visit them. We can't know of them, they can't know of us.
If some alien civilization has been able to listen in on our radio communications, well for one thing they'd have to be withing a hundred or so light years, because before that we didn't have radio. We can't hear any intelligent radio signals coming from space, though we've spent many millions of dollars listening.