Thanks to Aristo for sussing out the hidden letters.
I perused my copy with a magnifying glass & found there is shading that is barely visible.
If anyone is still interested, they are in (row, column):
1, 14
2, 2 & 2, 9
3, 4
4, 12
5, 2
6, 13
7, 10
8, 7
9, 2
10, 8
11, 6
12, 4
13, 7
14, 8
Apologies for the confusion. Anyone figure out what No. 16 refers to?