I wanted to understand the chess engine comparison. What does this result matrix show? For example in the first row and second column, Stockfish vs Houdini, the result is 27-25+7-3=-16. I understand that 27 signifies Stockfish's number of wins+ draws, similarly 25 signifies that of Houdini. But what does "7-3" signify? and how is the result -16? 

And what does the blank in Row 1, column 7 mean? similarly in (6,11), (7,1), (7,10), (7, 12), (10,7), (11,6), (11, 12), (12,7), (12,11). Do they signify that those matchups have never happened? If so Where should I look for if I want comparison of such matchups?

This question may be weird, but please at least guide me where should I ask these questions if not the answer.
@muclux is right on the results. Check his comment. I'll answer what "16" mean.

Scroll further down on the page.



The number is the rating change. Stockfish lost 16 rating point to Houdini, similarly Houdini won 16 points from Stockfish (convince yourself by going to the Houdini vs Stockfish cell).