[AS3]Tonypa's tile based game - How do I use a bigger tilesheet?

Hello. I’ve used Tonypa’s tile based game-tutorial for AS3 in order to try making a game.
In the tutorial he uses a .gif with 6 different tiles. He uses actionscript to extract each of the tiles from the .gif. In the array that builds the map, he uses these numbers to define which tile to use where:

0 ( numbers below 100 are used for walls and stuff)

I thought that if I made my own tilesheet that had twice the height of his, I could simply write 106, 107, 108, and so on, in the array to make it put my newly added tiles on the screen. This however didn’t work very well. It seems as if it’s a bit more complicated than that. Perhaps I need to change the equations in some way? I have no idea how to change them though.

So, what should I do to make it possible to use a bigger tilesheet?
I’d be very grateful for any help.

private function getImageFromSheet (s:Number, ob:* = null):Bitmap {
            var tsize:int = ts;
            var sheet:BitmapData = tSheet;
            if(ob != null){
                tsize = ob.ts;
                sheet = ob.sheet;
            //number of columns in tilesheet
            var sheetColumns:int = tSheet.width / tsize;
            //position where to take graphics from
            var col:int = s % sheetColumns;
            var row:int = Math.floor(s / sheetColumns);
            //rectangle that defines tile graphics
            var rect:Rectangle = new Rectangle(col * tsize, row * tsize, tsize, tsize);
            var pt:Point = new Point(0, 0);
            //get the tile graphics from tilesheet
            var bmp:Bitmap =  new Bitmap(new BitmapData(tsize, tsize, true, 0));
            bmp.bitmapData.copyPixels (sheet, rect, pt, null, null, true);
            return bmp;