PHP code in Header.php

I placed the PHP code in my header.php file. When viewing my pages, only the first image of 13 images scrolls across the screen. It reappears after a few seconds as if it had displayed the other images. Any idea why this happens? I noticed a few others are having

http://wordpress.org/extend/plugins/image-horizontal-reel-scroll-slideshow/