Negative marks for mistakes I just got the grade for a problem sheet that we had to hand in. The grading of the TA seems really ... odd, to put it nicely (for example, 1 exercise consisted of 3 basic computations - I got the correct values on 2 of them, but on the third even though I plugged the good numbers in I just typed a wrong number for the final result for some reason and this "mistake" got me only half the marks for that entire exercise).

However, the following thing really baffled me, I have never encountered anything like this in my education so far: one of the problems had a maximum grade of 0 points (which I got). Furthermore, for making a mistake you would have ended up with negative marks. To me, this seems very unfair (basically taking points away from other questions which were solved correctly) and highly not pedagogical as I don't believe that students should be punished for making mistakes.

I was planning on bringing this up to the professor tomorrow, but I thought it would be good to get some opinions on this matter. Is this kind of behavior common? The field is Astronomy/Physics and the country is Netherlands.
I've seen such grading used for true-false and multiple-choice questions in an exam, where a right answer gained you points and a wrong answer cost you points, but I've never heard of a problem worth "nothing" that cost you points if you got it wrong.

Personally, I dislike such systems—I'd rather give credit than subtract for mistakes—but instructors often have broad latitude in the design and scoring of exams. Some schools do have rules with regards to specific situations (if I remember, there were some weird regulations regarding all multiple-choice exams at my old institution), but in the absence of those, professors are free to set grading criteria as they choose, so long as they are applied consistently.