Sometimes you will see classes listed for variable amounts of units, such as 3-5. It's not a typo, but it may mean different things!
When a course is listed with variable units (such as 3-5), it usually means one of two things:
The number of units depends on the amount of work you will do in the course. For instance, students enrolled for 5 units will write more papers than students enrolled for 3 units. If this is a true variable-workload class, the differences in workload should be explained in the syllabus.
The course is designed to allow undergraduate and graduate students to take it for different numbers of units. For example, CS 106A is taken by graduate students for 3 units, while undergraduates must enroll in the course for 5 units. The amount of work is the same, but you must select the option appropriate to undergraduates in order to receive a grade. Often when this is the case, the unit options for graduate and undergraduate students will be explained in the course description on Explore Courses, usually by searching for the course and then clicking on the blue "Schedule for [course]" link.
Whatever the situation, it’s always good to check with the instructor when it’s a variable unit course and ask what the difference means. You can adjust the number of units you are taking through Friday of Week 3 (the Final Study List Deadline), so make your decision and make sure your record in Axess is correct by then.
When you are enrolling several weeks in advance, it's fine to pick a temporary number of units, just be sure to adjust it later as you get more information.