Alum here. If memory serves me right, there are spots reserved for incoming students in most (if not all) entry-level courses. These spots are currently unavailable to other students, so do not appear in the totals for courses. When it comes time for incoming students to register, the maximum number of seats in each class will likely be much higher.
For example, in Spring 2018, ENGL-135 had 18 seats in a section. Meanwhile, on the Fall 2018 course schedule, we see that the maximum seats for ENGL-135 is currently listed as 13. I do not believe this is the “final” maximum - I suspect 5 additional seats in this course will open for incoming students.
As for registering for courses, I had no trouble getting the courses I wanted in my first semester. If one has any difficulty getting the courses he/she wants, I would highly advise joining the waitlist, attending the first few classes, and talking with the professor about wanting to take the class. In many cases, this is a winning recipe!