Imagine genes like a deck of cards. Lets say you get 26 black cards from your father and 26 red from your mother. When your daughter is born, she gets 1/2 of her cards from you and 1/2 from her father. Lets say the father has blue and green cards. She could get 26 green cards and no blue, or 13 of each.
Lets assume that the Italian genes are the red cards. She could draw 23 red cards and no black cards or 23 black cards and no red cards, or some combination in between. If she drew all read, she would have 43% Italian, if she drew no red, she would have 0% Italian.
Theoretically, lets say your mothers parents are one Chinese and one Italian and your father's parents are the same. It is possible that you could have 100% Chinese DNA or 100% Italian DNA if you inherited through your father the genes of only one of his parents, and through through your mother the same.
Hope that makes sense.