@ProfessorPlum168 The non-majors would be able to sign up for the waitlist, but it is locked until the class begins. If there are remaining seats after accommodating the majors, then finally the non-majors will be officially enrolled in the class.
In case of having significantly more students on the waitlist vs. available spots, the instructor may take attendance in the first few lectures and drop anyone who misses. I’ve had a case where almost nobody dropped and it was actually up to the professor to change the lecture hall to accommodate the rest of the students.
Overall, high waitlist numbers or reserved for majors isn’t something I would feel discouraged at all, but simply a matter of do I really want to take this class or not. Attend the classes, perhaps chat with the professor a bit after class, and one way or another you can find a way to enroll.