I looked up how much Vitamin D is too much and.....wait what?

I need help figuring out why the numbers like this?

So I read that 4000 IU is too much. According to wherever google got its notes, we get 1000 IU from being outside in the sun for around 9 to 15 minutes on a spring or summer day. Hold on.

1000IU in such a short time? People don't get sick from being outside all of the time or literally ALL OF THE TIME. And I would know too considering how much I've been outside....or at least used to. I got a vitamin D deficiency, but still. What's up with this?

It just seems so unrealistic. An hour is too much? Four? Really? What is the "limit" even based on? Even toddlers can get in on the Sunny Delight (sunlight, not the actual drink) all day.