The analysis of a text #1

The narrator recalls his childhood; he is now in custody by his stepfather in his room.
He had been living with his mother, Peggotty the only maid of his house, his very stern stepfather Mr. Murdstone, and Mr. Mudstone's eccentric elder sister Miss Mudstone in his late father's house when he was forced to go Salem House, the boarding school near London.
Now he came home after the stay during a semester.
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His mother grumbles to Peggotty about Mr. Mudstone as she criticizes Peggotty.

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"No, Peggotty," returned my mother, "but you insinuated. That's what I told you just now. That's the worst of you. You'll insinuate. I said, at the moment, that I understood you, and you see I did. When you talk of Mr. Murdston's good intention, and pretend to slight them ( for I don't believe you really do, in your heart, Peggotty), you must be as well convinced as I am how good they are, and how they actuate him in everything. If he seems to have been at all stern with a certain person, Peggotty?you understand, and so I am sure does Davy, that I am not alluding to anybody present?it is solely because he is satisfied that it is for a certain person's benefit. He naturally loves a certain person's good. He is better able to judge of it than I am, for I very well know that I am weak, light, girlish creature, and that he is a firm, grave, serious man. And he takes," said my mother, with the tears which were engendered in her affectionate nature, stealing down her face, "he takes great pains with me, and I ought to be very thankful to him, and very submissive to him even in my thoughts, and when I am not, Peggotty, I worry and condemn myself, and feel doubtful of my own hear, and don't know what to do."
[David Copperfield by Charles Dickens]
I'd like to know if "that" clause is an object of "understand."
Thank you in advance for your help.