Could you please take a look at the following sentence:
You must not know about me.
Technically, it means “You are not allowed to know about me.”
But it seems, it can also mean “You obviously don’t know me.”
Would you agree?[YSaerTTEW443543]
TOEIC listening, photographs: A child in a cart[YSaerTTEW443543]
Hi Torsten
I don’t agree with that statement. 
Yes, the word must is used to indicate high probablility or a logical conclusion as well as necessity or obligation:
dictionary.cambridge.org/define. … &dict=CALD
Your second interpretation of must is also normal, standard usage.
Amy
Hi, Torsten!
As I see it may also mean
“Probably you don’t know what happens with me”, as in the sentence
“There is something strange about the way things are going here”, or “There’s something wrong about him”.
That’s just my humble opinion and it can be mistaken.
Thorsten, I largely agree with you about the first meaning but I would change the wording of the interpretation to ‘You (should not) (best not) know about me’. This means that it is best for you or me or both of us if you don’t know about my situation. Your knowing about my situation could lead to trouble.
Hi Torsten
I sense a misunderstanding here.
I wrote the sentence in the quote in reaction to your saying “technically, it means” since must has other meanings and usages (as you pointed out).
Amy