It means they don't know anything about you/haven't read your ABS or C.V. prior to interviewing you and won't ask you specific questions on these. Essentially, the interviewers are blind to your previous experiences, GPA, MCAT etc.
Actually, for PS, I try NOT to focus too much on the nitty-gritty and try my best to extract what concept/s they are testing me in the passage. I skim the passage and highlight some key things (e.g. numbers, new concepts or laws given, etc.). I think the trick is to understand that a lot of the time a really dense experimental passage is used to try and confuse students and it is those who succeed in extracting pertinent information and understanding which PS concepts are being tested that score the highest. So in other words, read the passage carefully but don't worry if you don't understand everything since they may not even test you on that part of the passage and most of the questions can be answered without passage info.
Just try and remember that each question is testing you on something that you already know (a concept or combination thereof) or is in the passage (in these Q's are usually quite obvious), it just may not be immediately obvious to figure out.
Be careful of using this technique for BS though as most of the passages there require in-depth understanding--especially if they are experimental.
Also, take my advice with a grain of salt as I'm no PS expert but I usually score in the 11-12 range.
Maybe some other premeders can chime in on their techniques/strategies as well.