Reducing Mobile Blog Summary Block Size

Hey all,

I am trying to decrease the size of two blog summary blocks on mobile with the following CSS:

@media (max-width: 640px) {
  .fe-6393883df61d0ae775ad84ee {
    grid-template-rows: repeat(5,minmax(24px, auto));
}
}

This is successful when I have the CSS editor open, but the changes aren't applied once I leave the CSS editor, leading me to believe that there is some kind of error. I want to decrease the size of the blocks as well as the distance between them once the size is decreased. Can anyone see why this might not be working?