Imaged not centered on certains devices in layerslider

Hi,

I really struggle with something which I’m sure is really simple to deal with but I cannot find the solution.
On my website I have a slider buil with layer slider you can see it here : http://www.calliframe.com

The problem is when I watch it on my powerbookpro retina 17″ the little round that fall in the first slide is centered but on a bigger screen it’s on the left. It’s the same with the second slider. Everything is moved on the left.
Is there a way to make my elements centered on every device??

I have read that sentence in the settings: “px) This feature is useful if you are using a full-width slider and you want to avoid stretching your layers across the full viewport horizontally. Just specify a custom width in pixels, and the slider will create a centered inner area to place your content into that. Note that this feature is working only with pixel-positioned layers, but you can still use the value ‘50%’ if you want centered positions.”

but I don’t understand it. Can anyone have a look at the screenshot where my settings are define and tell me if I do something wrong? I’m sure it’s simple to correct but I find the answer nowhere.

https://www.dropbox.com/s/w84gxi31coxi6rm/LayerSlider%20WP%20%E2%80%B9%20wordpress%20et%20webdesign%20par%20Christelle%20Bourgeois%20%E2%80%94%20WordPress%202013-10-17%2014-38-35.png

Kind regards,

Chrys.