I really liked the program, but unfortunately did not make an isometric map with square shape 1920x1920 or 2400x2400. I use tiles 48x24, and the size of map becomes 4800x2400. In the corners of the map cells are not available, and I need to fill the entire map tiles.
That is what you get when you do isometric projection of a 2D tile map. If you want a plain rectangular map but still use isometric tiles, you should probably choose “Isometric (Staggered)” when creating your map. That way the coordinates are a little strange (due to the staggering), but the shape of the map remains rectangular.