JSFiddle - React, Tailwind, and code Playground

HTML

<ol>
    <li>a</li>
    <li>b</li>
    <li>c</li>
    <li>d</li>
    <li>e</li>
    <li>f</li>
    <li>g</li>
    <li>h</li>
    <li>i</li>
    <li>j</li>
</ol>

CSS

ol { counter-reset: item; }
ol li {
    display: block;
    counter-increment: item;
}
ol:after {
    display: block;
    content: "Number of items in this list: " counter(item) ".";
}