I think the word "overstand" is just something somebody made up in order to sound "cool" or more "in touch" or "learned" about a subject/matter as if it instills/signifies some type of so-called higher understanding, some kind of "enlightenment" that, allegedly, understanding, in itself, supposedly cannot render.
Understanding is understanding is understanding. It is comprehension. It is being aware and cognizant. It is interpreting and defining.
Now, yes, there are different "levels" of understanding, deeper and more complex, mentally and spiritually; but "overstanding" something, to me, just implies that one may "over" process something, making it into something it is not.
Just because one word uses "under" doesn't mean that it is, in any way, deficient/below standards in construction, and "over" doesn't meant that it's better or more "improved."
So, if my "understanding" is not adequate. I'd rather just work on uplifting my mental processes. Cuz "overstanding" sounds dangerous to me.