24. Recipe markup review

A partially elided recipe:
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Pizza</title>
<meta charset="utf-8" />
<meta name="category" content="main"/>
<meta name="credit" content="Paul Grosso"/>
</head>
<body>
<main id="main">
<p>Serves <span id="serves">4</span>.</p>
<div id="ingredients">
<ul>
<li x-quantity="3" x-units="cup">3 cup <span>flour</span></li>
<li x-quantity="1" x-units="tsp">1 tsp <span>salt</span></li>
…
</ul>
</div>
<div id="directions">
<ol>
<li>Put dry ingredients into food processor (preferably, though not
…
is about <span x-quantity="12" x-units="in">12 inches</span> in
diameter or so.)</li>
…
</html>