Remember the following:

1) GMAC (the guys who make the test) are the best people to know the algorithm so GMATPrep is any day better than *any* other test (MGMAT, Kaplan, Veritas Prep, Knewton etc) in terms of both quality of questions, as well as the scoring range. "MGMAT seems pretty accurate" allows you to make 8+ mistakes and still you land up with a 44+ hmmmmmm........very unlikely on the actual GMAT.

2) 4 incorrect answers can certainly yield a 44 but remember that the verbal scoring system is vastly from the quant scoring system. Though both of them are out of 51, it is very rare of have a verbal score of 45+. I have attempted GMAT multiple times and have rarely scored below 50 in Quant while I have exceeded 45 only once (though I am an verbal instructor ). This is because in quant you can afford making a few mistakes and still get through with a 1 or 2 point drop. Verbal is brutal in that aspect - just a few mistakes and it drops to 42-44 in no time. However remember that a Q50 V44 would still give you a 770 - a very, very good score. So don't worry

3) You can read about GMAT algorithm to understand how it works. I have written a bit about it here (this is 4 years back so some of it might be a bit "dated"):
https://www.crackverbal.com/blog/gmat-sc ... ied-partly
However, remember this: on the real test it is futile to answer questions *based* on your understanding of the algorithm. All this information really means little while you take the test since you should try to solve each question to *the best of your ability*. This means there is no point in guessing if a particular question is experimental, or wasting too much time just because a question appeared in the first 5, or not taking the questions that come towards the end seriously. Solve each question on its own merit + what you can and you will do well.

Arun