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)
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?”
“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?”