2d array and index looping

Hi everyone,
I have a 2d array of cells (like a chessboard), the problem is that it seems that it keeps counting the indexes despite the edges of the grid.
This is happening in vertical but not in horizontal.
I don't understand why is counting that way and how to avoid this.

here is the code

for (int i = 0; i<ROW; i++) {
        for (int j = 0; j<COL; j++) {
            
            if (cells[i][j].rect.inside(x, y)) {
             
                if (cells[i][j].getPossible() == true && cells[i][j].cellval == " ") {
                    clickCounter++;
                    refreshPossible();

                    cells[i][j].setActive(true);
                    cells[i][j].cellval = ofToString(clickCounter);
                    <img src="/uploads/default/original/2X/e/e1e139b0b69f30a69a1636c903f14179abfe9303.png" width="300" height="500"><img src="/uploads/default/original/2X/4/4876d1c1b3909c9dc1bc4e3f1505f34350c5444e.png" width="296" height="499">
                    cells[i][j-3].setPossible(true);
                    cells[i][j+3].setPossible(true);

            }
            
        }
    }
}

I am attaching the images. The yellow cells are the one I am referring about (index +3 and -3)
any idea about this?
thanks.

Image may be NSFW.
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Screen Shot 2015-10-25 at 14.57.48.png600x1000 5.67 KB

Image may be NSFW.
Clik here to view.

Screen Shot 2015-10-25 at 14.58.25.png592x998 5.68 KB