Thumbnail size is not changing

Hi,

I Installed the plugin, created a new gallery, added it to my page and the gallery is working but it’s too small, the width of a typical page let’s say 1200px, my gallery width is 488px, too small.

Now it’s small because I choose: 2 Images per page in the gallery settings.
so the gallery is container is full width, but I don’t have control of the images that are showing, I thought I could set that in the settings page. I assumed I could change something like each thumbnail in percentage, in this case I need each one to be 50% of the container.

Are you aware of that issue?