Hello vincentwp,
Thank you for your question about galleries. It sounds like you are noticing the page’s responsive layout. This means that the gallery will looks slightly different in scale and position depending on how you’re viewing it.
For example, the layout will look different in the preview window of the page editor than it will on the site. Likewise, the site will look different on a standard monitor than it would look on a phone or tablet. This feature ensures that the site will display attractively on different devices.
Best,
Christopher M.