Changing height of mobile home page banner slideshow gallery

Site URL: https://www.whitbycollegiate.school.nz/

Hi there, I want to reduce the height of my slideshow gallery on the homepage banner when displaying on mobile by about 50% but I can't work out how to change this.

Add to Design > Custom CSS

/* resize slideshow */
@media screen and (max-width:640px) {
    #home-1 .gallery-block {
       .sqs-gallery-design-stacked, & {
    height: 300px !important;
}
.sqs-gallery-controls>a {
    top: 25% !important;
}
    }
}