See, the way Dutch designed his system, it doesn't count as a miss that Yellowstone didn't erupt. Instead, he'll assign it a very arbitrary timeline somehow connected to the orbit of a planet, and then each time it hits its "trigger date" it may happen again. Again and again and again... it's a perfection of designing a system around confirmation bias.
Let me give you an example. Say I say the planet is mercury, the day is first of June. I pull a random prediction out of somewhere "Squirrels will fall dead from the sky!". June first rolls around, no dead squirrels. So then there's 88 days until the "triggerdate" rolls around again, at which point it's supposed to happen again. So each "miss" has been handily converted from a "miss" to a "watch the next trigger date".
That's how HDD is put together. It's also worthless, but then, everyone is already well aware of that.