I bundled people by supervisors and requests I got by email; I did my best.
Students need to attend both days, unless they tell me beforehand why they cannot attend (another course is more or less the only reason acceptable).
As you see, the schedule is tight, and therefore 10min will be 10min. The break will be short since we have 11 students per day, and I had counted on 10 (had omitted students from previous years starting now).
Best is if you bring a USB with your PDF (or PPT) and you use the room computer. Upload your presentation before it starts or during the break.