I still do not understand why the first 10 questions must matter more than the rest. I agree with everyone here who says that you will end up hurting yourself more (through wasted time) than helping yourself by spending all of your time on those.
The first few questions will cause your score (if there was such a thing as a score after a few questions) to swing widly because the test has no data on you yet. So, every question will have a big impact on your score. But, if you get the first question wrong, it is not like the test knows for 100% certain that you are in the bottom 50 percent. What if you just made a dumb mistake, and your true level is 760+? After answering enough questions, that should emerge.
By the end of the test, a CAT should still be able to determine what your real level is, regardless of how you did on the first few questions.
I see what you're saying. I believe that you can miss 1 (maybe 2) of the first ten as long as they are not questions 1/2 or 2/3. If you hit two wrongs in a row starting out, you are throwing yourself in the 400 range and even by making 10 questions in a row right, the CAT will not adjust upward as dramatically. Further, even if you happen to get 20 in a row correct, you no longer have the opportunity to answer 20 700+ questions correct. Others, however, have had that opportunity and since the final score is a percent'ILE' score. You will not get a 760 if you missed 2/3 of the first five questions. It just won't happen. 710.. maybe. 760... no.