<div class="transform">42.48%</div>



    //转化
    .transform {
      position: relative;
      width: 70px;
      height: 26px;
      background-color: #dcdfe6; /* 长方形的颜色 */
      display: flex;
      justify-content: center;
      align-items: center;
      font-family: PingFangTC-Medium;
      font-weight: 500;
      font-size: 14px;
      color: #303133;
    }

    .transform::after {
      content: "";
      position: absolute;
      top: 26px; /* 三角形位于长方形下方 */
      left: 0px;
      width: 0;
      height: 0;
      border-left: 35px solid transparent;
      border-right: 35px solid transparent;
      border-top: 6px solid #dcdfe6;
    }

参考：

纯CSS画基本图形（矩形、圆形、三角形、多边形、爱心..）_css结构框图怎么画-CSDN博客