Zenphoto creates as many images as it needs, as I said. How many depends on your theme. If you have thumbs and a bigger images that makes two, If you have album thumbs of another size that are three, if you display images elsewhere that can be more. If you switch sizes for testing, it creates again new images.
May I suggest that you take the time to look through the administration backend first before asking questions? There are buttons to delete the image cache both on the overview page and on each album edit page.