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In an Oxford dictionary, ‘must have –ed participle’ is used for supposing a past event.

He must have known (= surely he knew) what she wanted.
I'm sorry, she's not here. She must have left already (= that must be the explanation)
(Advanced Learner’s)

However, a case below seems to have some different meaning. Although, yet, I do not have found the explanation, from a grammar textbook for Korean language, I guess the case seems to express an awareness of realization, perfection, or the continuity of the perfection at present with a past form. Can my guessing be right, or am I to learn about some other explanation?

“Jane,” he recommenced, as we entered the laurel walk, and slowly strayed down in the direction of the sunk fence and the horse-chestnut, “Thornfield is a pleasant place in summer, is it not?”
“Yes, sir.”
“You must have become in some degree attached to the house,—you, who have an eye for natural beauties, and a good deal of the organ of Adhesiveness?”
(Jane Eyre)

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It's still in the past. – Kris Apr 1 '13 at 5:05
It's the same: You must have become attached (= surely you became attached) – Jim Apr 1 '13 at 5:23
up vote 1 down vote accepted

Your guess is correct. The present perfect can be used:

1.) to refer to a completed action in the past.

  • She's left.

2.) to refer to a state that began sometime in the past and continues into the present.

  • She's become attached.

The same applies when the present perfect is used with "must" to indicate a deduction:

  • She must have left = I deduce that she has left. [The leaving is completed.]

  • She must have become attached. = I deduce that she has become attached [and still is].

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