> I don't think I've ever seen the 20mcg rec

The 20mcg rec (the wrong rec) is quite literally on every single nutrition label in America that has Vitamin D. Maybe you haven’t noticed it. Surely you’ve seen it if you’re in the U.S.

https://www.fda.gov/food/nutrition-facts-label/daily-value-n...

> What was the math error that led to this? And I'm curious now how to get 8000 IU. Just take a bunch of pills all at once in the morning?

Read the paper I posted. And it is easy to find 5000iu and 10000iu capsules at a drug store.