OCJP6 and NavigableMaps

Hello,
Two largely unrelated questions on the OCJP6 exam.

1. Somebody told me that for the 60 questions you answer on the exam, Oracle don't mark about 5 of them, so you only get marked on say 55 not 60 (meaning of course each question is worth much more in percentage). Can somebody clarify this and hazard a guess as to why on earth this is the case?

2. Can somebody tell me whether I need to learn about Map.Entry for NavigableMaps and all the related methods? I was doing some whizlabs stuff and there are a lot of questions on NavigableMaps and many include topics on methods/usage that is completely missing from the Kathy OCJP6 book, one such thing is Map.Entry (to name but one of many omissions/questions I'm getting). To be honest, I have a copy of OCJP5 book and for all the alterations to the 5 book you can spot them a mile off as they are clearly very hurriedly written and contain sparse detailed information unlike the rest of the book.

Thanks.

How much trustworthy is that somebody?