When I vote to close a question that is duplicating another one, I get a list of questions with some numbers.
What is their meaning?
Having just voted on another duplicate, I now have a more conclusive answer. The numbers on the left are "the combined score of question and answers" (my cursor was hovering over the box, but you can't see it in this screenshot):
The numbers on the right (again, my cursor was hovering over them but you can't see it here) give the number of times a question has been linked to, or voted as a duplicate: