An upper bound for the background rate of human extinction

If this is accurate, it's pretty scary:

https://www.nature.com/articles/s41598-019-47540-7?utm_source=commission_junction

But this section is confusing:

"Using only the information that Homo sapiens has existed at least 200,000 years, we conclude that the probability that humanity goes extinct from natural causes in any given year is almost guaranteed to be less than one in 14,000, and likely to be less than one in 87,000. Using the longer track record of survival for our entire genus Homo produces even tighter bounds, with an annual probability of natural extinction likely below one in 870,000."