Actually, I read this documentation before posting my question. I didn't see anything in this section about editing or changing a dataset. My mistake. Not blaming anyone else. Just saying that it is possible to read the documentation and not realize that the method of creating a dataset is the same as editing it.
Also, "media" doesn't have any child datasets, so I'm not sure why you think that will make any difference.
Yes, you are correct, it has no children. I was referring to the prefilled values for this form.
In my example, the pre-filled value was "0" for the dataset quota and "1T" for the dataset+children quota. In this case, the quota for the dataset was unlimited, so changing it could not have any effect; I had to increase the quota for the dataset+children in order to give the dataset room to grow.
Again, thank you for pointing me in the right direction. I posted my comments just to help anyone else who, like me, couldn't figure out how to increase the quota.