"But" ...

When I see "but"s in a sentence, sometimes it can freak me out (or stun me) , so to speak. For example:

(A) I have all but 4 apples.
(B) I have nothing but 4 apples.

The above two sentences may not freak me out, as they are not complex sentences. But then, this really freaks me:

I have but 4 apples.

Does this imply sentence A or sentence B? How many apples? You get what I mean?