discourse/app/assets/stylesheets/common/components/relative-time-picker.scss

.relative-time-picker {
  display: flex;
  flex-wrap: wrap;

  input[type="text"] {
    flex: 1;
  }

  .select-kit {
    flex: 1;
    width: auto;
    margin-left: 5px;
  }

  &:last-child {
    margin-right: auto;
  }
}