How to use CSS to write different styles according to sub-elements

div {
    &:last-child:nth-child(1) {
      // Related styles}
}

div{
    &:nth-last-child(2):nth-child(2) {
    
    }
}

     <div class="box" v-for="(item,index) in list" :key="index">
          <div class="header">
            <img :src="item.userImage" alt="">
            <span>{{item.name}}</span>
          </div>
          <div class="content">
            <img :src="v" alt="" v-for="(v, i) in item.imageUrl" :key="i">
          </div>
          <div class="bottom">
            <span class="left-icon">{{item.createTime}}</span>
            <div class="right">
              <img src="./img/6.1.png" alt="">
              <span>{{item.fabulousNumber}}</span>
            </div>
          </div>
        </div>

.box {
      padding: 0.26rem;

      .header {
        display: flex;
        align-items: center;

        img {
          width: 0.58rem;
          height: 0.58rem;
          margin-right: 0.17rem;
        }
      }

      .bottom {
        display: flex;
        justify-content: space-between;
        align-items: center;
        color: #999999;
        font-size: 0.17rem;

        img {
          width: 0.17rem;
          height: 0.17rem;
        }
      }

      .content {
        display: flex;
        margin: 0.17rem 0;

        img {
          flex: 1;
          height: 1.37rem;
          width: 0;
          margin-right: 0.09rem;
          &:last-child {
            margin-right: 0;
          }
          &:last-child:nth-child(1) {
            height: 2.75rem;
          }
        }
      }
    }