Fine tuning is the result of restrictions and requirements.
For our universe to have specifically us in observing it at this very moment, it would need to be fine tuned with the exact properties it has.
Any other tuning would only be observable, by potential beings that could observe it. It would be impossible for us to be exactly as we are, if we were in any other universe.
Ergo; the probability of our universe being precisely exactly the way it is..