해리포터 불의잔 읽다가 이해가 안 되는 부분이 있어서요

몰리가 일반 우편부에게 편지를 보내서 버논이 화가 나서 해리를 몰아붙이는 장면인데요

Uncle Vernon looked as outraged as if Harry had just uttered a disgusting
swearword. Shaking with anger, he shot a nervous look through the window, as
though expecting to see some of the neighbors with their ears pressed against the
glass.

"How many times do I have to tell you not to mention that unnaturalness under my
roof?" he hissed, his face now a rich plum color. "You stand there, in the clothes
Petunia and I have put on your ungrateful back -"

"only after Dudley finished with them," said Harry coldly, and indeed, he was
dressed in a sweatshirt so large for him that he had had to roll back the sleeves five
times so as to be able to use his hands, and which fell past the knees of his
extremely baggy jeans.

두번째 단락에 "You stand there ~ ungrateful back -"
이 부분이 이해가 안되네요
뒤에 이어지는 내용으로 봐서 옷과 관련된 내용 같은데...
답변 부탁드립니다^^