JSFiddle - React, Tailwind, and code Playground

HTML

<div class="box box-1">
  <div class="block">
    <div class="item"></div>
  </div>
  <div class="block">
    <div class="item"></div>
  </div>
  <div class="block">
    <div class="item"></div>
  </div>
</div>
<div class="box box-2">
  <div class="block">
    <div class="item"></div>
  </div>
  <div class="block">
    <div class="item"></div>
  </div>
  <div class="block">
    <div class="item"></div>
  </div>
</div>

CSS

.box { counter-reset: item; }

.box-2 .block { display: contents; }

.item {
  counter-increment: item;
}

.item::before {
  content: counter(item);
}