This is only a written short form of assistant — a person who helps someone in a job. You see it in titles on name cards, email signatures, and office doors: Asst. Manager, Asst. Editor, administrative asst. People do not say “asst” out loud; they say assistant, or they use the full title. It is a paper-saving label, like Dr. or Prof., not a spoken nickname. In schools and companies here, it almost always means the helper role, not a student or a machine. Though actually, some workplaces now write the full word because the clipped form can look careless. If you are writing a formal letter and you have room, assistant is safer; if you are copying a title from a card, keep asst. as they printed it.