Hi brnkrc, I am not quite sure what you mean ... your slideshow looks too big? The size of the slideshow will depend on the screen size that is viewing them, and the dimensions of the uploaded images. Do you have a link?
I think perhaps your problem is that on your start page you have set up the slideshow FILEMOD? This module does not scale images like inside the gallery ... Try changing your start page from FILEMOD to normal GALLERY mode ... Then you can still set a slideshow by using folder parameters instead.
https://www.photo.gallery/documentation/folder-parameters/ (scroll down to the slideshow example).