Multidimensional array in C

Hey, Im having trouble understanding how this function prints out this board. mainly how the 2d array is equal in 1 or 2 or 3 or 0.

Code:

---

void drawboard(int board[6][7]){
    int i;
    int j;
    printf("  1  2  3  4  5  6  7  \n");
    for(i = 5; i >= 0; i = (i - 1))
    {
        for(j = 0; j < 7; j = (j + 1))
        {
            printf(" | ");
            if(board[i][j] == 1)
            {
                printf("X");
            }
            else if(board[i][j] == 2)
            {
                printf("O");
            }
            else if(board[i][j] == 3)
            {
                printf("4");
            }
            else if(board[i][j] == 0);
            {
                printf(" ");
            }
        }
        printf(" | \n");
    }
    printf(" ----------------------------- \n");
}

---

This function prints out a board for connect 4, and im trying to update it in a turn based way by calling it after I ask a user for what column he wants to drop the piece. So he can choose columns 1 throught 7.
So Im going to update my array to
board[]["whatever column he chose"]. I dont know what to do for the row.
And then the function will take the board and hopefully drop the piece

Look at the incremental sections of each for loop. Math involved be it 'i' or 'j' would represent the total value of the rows and columns. Thus, the 'if' statement would return true if the total value of the 'i' + 'j' was equal to either 1, 2, 3 etc..

Of course, this is just a guess at what you mean as there is no other code present. I am taking on belief the sum values of each calculation would determine where the piece would drop.