have a question regarding the calculation of scores

Yes, take a look at some of my previous posts. The test is not scored based on percentage correct. The algorithm scores based upon the difficulty levels of the questions you answer. Almost everyone gets approximately half of the questions right and half wrong - it's only below about a 300 and above about a 720 that this starts to skew away from 50/50. And even those of us scoring in the 99th percentile are getting a decent number of questions wrong.

However much you study, you will not get all of the questions right. In fact, you will get a large number of questions wrong - and I can say that having no idea what score you will get b/c it's true for everyone. It's important to understand that before you go in or you will get psychologically messed up and your performance will suffer.