There are six different 6-digit positive integers that add up to a seventh 6-digit integer. Interestingly, all seven of these numbers consist of combinations of only two different digits. That is, only two different digits are used to write the complete set of seven numbers--the same two digits in each number.
So far you can't deduce what the numbers are, but if I were to tell you that seventh number, that is, the total, you'd know what the other six numbers were that made up that total.
What are the seven numbers?
From Enigma No. 1702, "All the sixes",by Ian Kay, New Scientist, 16 June 2012, page 32.
(In reply to re(5): IMHO - STILL REDUNDANT
I just wanted to point out that the new text (post #28) makes a more interesting and by far more challenging puzzle than the original one , since it leaves the task of finding the sum to the solver , rather than spelling it out in the problem.
Regarding the word "unique" one can find a better expression within the scope of the new text.
Having said that and assuming you understand the quality of the new text (improved,re-worded, explicitly explained, if you wish) I consider further correspondance counter-productive.
BTW the horse is not dead, it is alive and kicking.