I've used that program. Â I could never get the export functionality to work properly, so I would just open up the "Preview" application (should be in your Applications folder, although I've got it on my dock since I use it so much), go to File->Grab->Selection, then just select the area of the map I wanted to export. Â
Also, you have to make sure that you import tilesets as the right grid size or they will be messed up. Â