Image Sequence Skips First Image?

I made an image gallery, and I used a script to put them in an array, so people can browse through them using previous/next buttons. I think it may be a very oldfashioned script, but I don't know anything about javascript, and this one seemed simpler than others to modify.

I added a function that shows how many images there are and the number of the image you are seeing (photo 1/6 for example)

The problem is that the script seems to skip counting the first image, it calls the second one 'photo 1/6', doesn't allow you to go back to the first and stops at the fifth. I tried to add a window.onload function, but I think I did it wrong, or it doesnt work because of other scripts that are also loaded on the page (JqueryBeforeAfter).

Here is the script I used:

Code:
<!-- script created by : THeMaRTy -->
<!-- website: http://marty.excudo.net -->
var count=0;
var link_array = new Array();

[Code]....