(In reply to I must be missing something
...I must be missing something... No, you did not.
It was my fault, resulting from not trying to solve my own puzzle.
As you see, I have posted a corrected version, hoping it is TOTALLY OK.
Re your lists:
1.The 2nd list is meaningless. Bob made his remark after evaluating Gra's age.
2,. 1st list: the same triplets appear numerous times.
Actually , the generic triplet is x,15-x, N, within the limitations of the text.
Thank you a lot for your remarks.