First of all, I haven't seen the tiny square before, what does it mean? Just "and"? I'm also curious as to who (which book) uses this notation.

When you write , then you don't get to consider the right sets. The elements in T are A, B, C, D and E, so the set is necessarily a subset of , no matter what the condition for the set is.

I would write

where I'm trying not to worry about what it means, when you say that the number 1 in A is not the same as the number 1 in B. The important thing is that the first six elements of A are exactly the elements of A that are less than 7, and likewise for C, D, and E.