.rc-slider-mark-text {
    position: absolute;
    display: inline-block;
    vertical-align: middle;
    text-align: center;
    cursor: pointer;
    color: #999;
    width: 7%;
}
@media (max-width: 600px) {  /*600px si fuera solamente celular */
  .rc-slider-mark-text {
    width: 15%;
  }
  .rc-slider-mark {
      font-size: 8px;
  }
}