That didn't sound right, my experience that depending on luck and season, somewhere between 50 and 90 % of big mushrooms I come across in a forest are poisonous or at least disgusting. I admit it's a very wild estimate and I'm very far from knowing all the mushroom I come across, but still, that seems like a big contradiction. So I followed your link to the primary article.

I suspected that they might only count potentially lethal mushrooms, but no, it indeed seems they count even those that only make you nauseous. The problem is in the other number. The 100 000 means all funghi, it includes for example all yeasts. Most funghi don't create mushrooms that anyone would consider picking. So the ratio you calculated below is WAY off.

I would also like to note that the number 100 seems to come from a very simple PubMed search. Basically, if nobody wrote a paper about someone being sick after eating a mushroom, they wouldn't find it. I don't think that would mean that many foraged mushrooms would be missed, but it is a limitation worth knowing about.