It means you need to be there at least half hour before 8:30. I would say go earlier if you could, relax, aclaimatise yourself to the test environment. Load yourself with some water before the test ( usually they don't allow water inside the test center).
As for as preperations on Saturday & Sunday goes, I would highly advise against taking full test. IMO, taking full test won't serve you any purpose in the last moment. It will only drain your energy and teaches you very little. Instead, relax, keep yourself focussed. Go through your error logs, OG etc. Try not to do new problems they will only confuse you. Try to go to bed early on Sunday ( I had my exam on Monday morning 9:00AM too, I went to bed at 10:00 PM on the previous night)
Monday, get up early, try to do at least 5 questions in each sections and read through a couple of AWAs. This should be plenty to warm up your mind for the exam. Don't study anything for the last hour before the test. Listening to some music might help you calm down. Go with a positive attitiude and ace the test.