Thanks bee, did as you suggested and now I understand - the text that is being displayed forms part of the navigation bar but because the Alt & Title text is quite long, it's losing the navigation elements and the number that is displayed is the last digit of the number of slides. (I've just made the text even longer to push the number and separator off the page as don't want people moving the cursor over the image until the other issue is resolved.)
Any idea what is causing the navigation bar to disappear when the mouse is moved over the image area? It seems to display as long as the cursor is moving on the image area but disappears when there is no movement in the image area.
Is there any way to display the description as well as the navigation bar?
Is it possible to stop the audio track after playing once?