Hi @vlad90, you're right, but using an align div is the quickest fix and has a much higher success rate than using CSS (learnt this the hard way). Setting the margin to auto doesn't always work.
The CSS property you've mentioned has to remain the way it is to ensure the slideshow displays correctly. If you look at the CSS, the top section is rules I'd advise you don't change, important for structural purposes. The bottom section contains editable properties.
Using important rules is never a great idea, but when it comes to ensuring that the slideshow is not destroyed visually by themes or other plugins, it is essential we override all of the possibilities to provide a solution "that just works".
You could try putting a <div> around the slideshow and applying CSS 'margin: 0 auto;' to that, rather than altering the slideshow CSS itself. Alternatively, if you want to go "all out", you can disable the plugin styling in its "Settings" panel and use your own.