in the matrix:

[0 4 6]

[5 7 4]

[9 6 3]

i don't see any purely dominant columns, or recessive rows. so i don't see how they got the reduced matrix.

in your original matrix:

[2 0 4]

[1 2 3]

[4 1 2]

column 3 dominates column 2, so C will never choose that strategy over column 2, as it is worse in every case. that leaves us with:

[2 0]

[1 2]

[4 1]

clearly row 1 is recessive to row 3, so R will always prefer that strategy (row 3), resulting in:

[1 2]

[4 1].