You can't select your cores, labs, and tuts when you sign up for courses. SOLAR automatically generates a timetable for you that's conflict free. Whether you choose to stick with that one is entirely up to you.
You make your own mock timetable to have another option in case the one that SOLAR automatically makes for you sucks shit, which I assume yours does. When SOLAR re-opens on the 10th, go in and hand-pick the cores, labs, and tuts that you want, but bear in mind they're most likely full. If this is a huge problem you can talk to your course coordinator when you get to school and he/she'll manually put you in the sections you want to be in.
Mine's pretty bad too:
http://www.macinsiders.com/showpost....&postcount=105
BUT, I've got a sweet mock timetable for second semester so I'm gonna change that as soon as I can.