I used to have an outlook such that I'd probably have turned it to 90 and thought up some parameters to ensure survival of a fair variety of intelligent, healthy, considerate, and creative people to lead a new golden age.
But since I started watching a certain YouTube channel, I've rethought my perspective. It is the destiny of our species to one day spread across the cosmos colonizing countless star systems (I'd consider destroying ourselves before that point to be failure). And at that point, even if we've obliterated every single other species on this planet and even strip-mined the planet itself to nothing, it will in a way be a worthy sacrifice - we'd pay back our great debts to the countless creatures that lived before us by taking part in our little planet's blossoming from a nondescript rock to the seed of a glorious cosmic empire. And yes, there will be bumps on the way - heck, there might be another ten Dark ages before we make it - but if we ever make it at all, in my book it will all have been worth it.
So in short, as it stands now I'd leave the dial at zero.