Especially the set example is also just confusing for 7th grade kids (or anyone who doesn't already understand sets, really). It's technically correct to say that you can store the unique ingredients of a recipe in a set, but that's not an obviously useful thing to do (if you want to compose a shopping list, you need the quantities as well), so the example doesn't actually illustrate anything that helps make sets more intuitive to the student. I think many, if not most, kids of that age will also not even correctly parse the phrasing "list all the unique ingredients" (not to speak of the unfortunate phrasing "a set can be used to list all ..." while you're trying to illustrate the difference between a list and a set).