Make "Pairwise" description clearer

Somebody trying to do it found it confusing and so did I so I tried to improve the example a bit to be a bit clearer about why it returned 11.

seed/challenges/01-front-end-development-certification/advanced-bonfires.json

@@ -412,7 +412,7 @@
       "title": "Pairwise",
       "description": [
         "Return the sum of all indices of elements of 'arr' that can be paired with one other element to form a sum that equals the value in the second argument 'arg'. If multiple sums are possible, return the smallest sum. Once an element has been used, it cannot be reused to pair with another.",
-        "For example, pairwise([1, 4, 2, 3, 0, 5], 7) should return 11 because 4, 2, 3 and 5 can be paired with each other to equal 7.",
+        "For example, pairwise([1, 4, 2, 3, 0, 5], 7) should return 11 because 4, 2, 3 and 5 can be paired with each other to equal 7 and their indicies (1, 2, 3, and 5) sum to 11.",
         "pairwise([1, 3, 2, 4], 4) would only equal 1, because only the first two elements can be paired to equal 4, and the first element has an index of 0!",
         "Remember to use <a href='//github.com/FreeCodeCamp/freecodecamp/wiki/How-to-get-help-when-you-get-stuck' target='_blank'>Read-Search-Ask</a> if you get stuck. Try to pair program. Write your own code."
       ],