Correction

[bartholomew]

Hi
I was wondering if you could help me.
which of the two sentences is the more correct?

A. Did a member of staff tell you what a level of observation means?

B. Did a member of staff tell you what a level of observation meant?

[BigMac]

As far as I can tell, it could be either.

In the former, the question asks if you are aware, having been told, of what "a level of observation" means now/currently.

In the latter, it is asking if you are aware, having been told, of what "a level of observation" meant either in the past or in a particular, even current, context.

That's just my view - there are plenty of even more pedantic people on here who will now leap in to argue the true meaning/grammatical 'correctness' of the two sentences.

[Quizmonster]

As BigMac says above, both are perfectly correct, depending upon context.
It may well be, for example, that 'level of observation' is a widely known concept that has been used over a period of time. Thus the word 'did' in A must refer to a past occasion when the 'you' in the sentence was subject in some way to such observation. The question, therefore, asks whether the 'you' was told at that time.
B might also mean that, but it could also suggest that the whole definition of the concept of 'level of observation' has been changed. The questioner, in that case, wants to know whether the 'you' was aware of that alteration.
There are probably other interpretations, too, so you really need to ask yourself: "What am I trying to express here?"