"Q10b_1" is the variable that refers to the first item of the question (e.g., the item that appears first when the question is displayed), not the item that is ranked first.
What I would do is create a constructed list using the AddSorted function, like this:
AddSorted(Q10b)
Now you have a list of items, sorted by their ranking. You can reference them in your questionnaire using the ListLabel function.