EGMC,
Candidate A:
This person got 29 correct in the first 30 Q's...THEN got 8 wrong in the last 10. He obviously just guessed them- we do not want somebody who blags and guesses the answer... Plus, really he only got 77%
Candidate B:
gets the same score up to the point when the invigilator says "2 minutes", but then carries on as normal and spends two minutes on one question and gets it right, scoring 30 out of 40 = 75%
So although this person got a lesser score, still scored quite well, and out of those he attempted got a whopping 97%. He didn’t try to blag his way through but was more concerned with doing his job well or not at all
I have to say that I don't know. However, you could look at it the other way: Candidate A used his initiative and knew he wasn't going to finish all the questions if he worked them out, given two minute left, so he guessed them; while Candidate B steadfastly refused to change his plan in the face of overwhelming evidence that he'd not finish all the questions.
It's been a few years since I did the tests myself, and I remember I finished most of them, but I guessed the last few if I was running out of time.
As far as I know, it's just a straight total up the marks, rather than weighting any particular questions.