How does scss logic work in Rails?

Question

css

Good to everyone!
There is a project implemented on rails and just html layout.
There are style properties (scss) like this:

.elem {
  width: 15.9%;
  
  @media screen and (max-width: 1366px) {
    width: 49%;
  }
}

.elem_mod {
  width:  30%;
}

Markup: So, what should the block width be when the screen width is less than 1366? The idea is 49%. So it is in the usual layout, but for some reason the width of the rails is 30%. How so? Ruby 2.4.0 Rails 5.1.3 sass (3.5.1)
<div class="elem elem_mod"></div>