Problem with image sizes on supersized plugin

Hi,
I’m using the supersized plugin and it works almost perfectly. The only annoyance is that the very first time the first image is loaded, it is displayed in the wrong size. I’ve checked the style of the image using firebug and this is it:
style="height: 665px; width: 440.397px; left: 498px; top: 0px;"
in this case the screen size is 1436 (the height is correct).

Can anybody help me out with this, why is the javascript generating the wrong width and adding a left in there?

The site is https://www.ellivo.com/project_type/mixed-use/, if anybody wants to check it out.

Note: the problem doesn’t happen always, but I found that when I resize the screen (for example when using firebug the screen height reduces) it’s easier to get it to happen,

Any help will be appreciated

Thanks,