Caltech has required writings. One of them has a word limit of 200 but I quickly hit that word limit and I have more that I would like to say. At the end of the application, it says “If you need additional space, please explain using the upload function button below. Please do not attach a resume or upload research papers. Caltech will email you an application confirmation with information on how to upload research papers through your student portal”. Could I finish my response to that prompt here? Is that what it is saying?
If I were you, I’d stick within the required word limits (there’s a reason why it’s a limit, after all!) Concision is always good- cut your stuff down! I guarantee you that, no matter how tight you think your essay is, it could be even more concise.
I wouldn’t continue the essay in the additional space. But if you have more to say via separate essay, then have at it!