Where do you plug in that code?

And how do you think is better for you?

It can be Template Options > Custom Code > Custom CSS

or

Inside that Page Settings > CSS

I put it in the Page CSS, see pic https://tatumgrinblat.com/images/Screenshot%202024-08-10%20at%209.59.09%20AM.png

Still nothing.

This is the live site: https://tatumgrinblat.com

wrong CSS class name , not xs but sm in your case:

must be

.sppb-countdown-timer > .sppb-col-sm-3 {width: 23% !important;}

10% doesn't look good !!!!