Why not the red X's too?
I guess you have tried with red X's but you didn't have positive results,right?
So does it make sense to you that the red X's don't work but black O's do?
This pattern on the table layout, black O's and red X's,it's like playing TIC TAC TOE.
There are 4 red X's,2 of them including only red numbers and the other 2 including 4 red and 1 black.
Also there are 4 small black O's (or diamonds) ,the middle dozen has 1 big black X which is including 6 black numbers and 1 big red O which includes 6 numbers.
The smaller X's are red dominated,while the big X in the middle is totally black,the 4 small O's are black,while the big one inside the second dozen is red.
4 BLACK O PLUS 1 BIG RED
4 RED X PLUS 1 BIG BLACK
Why you think exists such symmetrical pattern on the table layout,pure coincidence?