I SWEAR, it's in the beginning of the book somewhere...Chapter 1 or 2 I think. The "For Dummies" series for testing/study guides always gives you some kind of preface as to what to bring to the exam and what to expect.
Obviously there's a section on scoring. It used the SAT as a comparison, pointing it the many similarities and differences. One similarity is that though you are timed, you do not get a "time credit" towards another section if you finish one early.
However...the biggest difference is that you are able to page back and forth in your test booklet with the SAT. The prime test-taking skill thus recommended for the SAT is to simply finish the questions you have an easier time with and come back to the harder ones later that you need to spend more time on.
The GMAT being all computerized has NONE, NADA, ZIP, of that. It's answer it or get off the page!
Have a decent sense of when one minute to 90 seconds have passed. Seriously. That's about all they want you to spend on a question. You spend too little, it looks like you breezed through it even if you got it right. You spend too long? You must be too slow according to these inhuman automatons who make this test up.
So yeah. Timing counts to these heartless b*stards!