Allocations made via KUSSS automatically check all dates and times to see if they overlap: If a class you wish to take overlaps with a class you are already registered in for more than 6 units (á 45 min = 270 min) or more than 4 class dates, you will not get into that class.
As a student, it is in your best interest to check the course schedule and devise a schedule in which classes do not overlap. Check "Stundenplan" to put together a course schedule of classes that will indicate if there is any overlapping.
See also KUSSS FAQs "How Can I View My Class Schedule (The Classes I Am Registered In)?"
Detailed information is available under Registration Regulations under § 8 Check for Overlapping.
If directly allocated to a class, the system will not check for overlapping dates & times