Examples:
http://gsd.umn.edu/ugrad/germanCourses.php
1001, 1002, 1003, 1004 would be the first four semesters of German language courses, while 3011 would be the fifth semester course (it lists German 1004 as the prerequisite).
http://guide.berkeley.edu/courses/german/
1, 2, 3, 4 would be the first four semesters of German language courses, while any of 101, 102A, 102B, 102D would be fifth semester courses (these have German 4 as the prerequisite).
Of course, a student with some knowledge of German may start in a course higher than the beginner course (1001 or 1 in the examples above).