div {
    width: 400px;
    margin: 10px auto;
    padding: 20px;
    font-size: 20px;
    position: relative;
    background-color: #d4d4d4;
}
div:first-letter {
    font-size: 0px;
    /*   OR   */
    visibility: hidden;
}
div::before {
    content: "1";
    position: absolute;
    top: 5px;
    left: -15px;
    padding: 15px 10px;
    color: #fff;
    background-color: #009688;
}