[xsl] xpath help?

["dvint@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

I have this xpath that returns more than one result

//a[contains(@filepath, 'preface.html')]/@newid

I thought adding [1] to it like this would get me the first entry, but 
the result doesn't change

//a[contains(@filepath, 'preface.html')][1]/@newid

Here is an example of the file I'm processing


<nav>
	<div class="coverpage">
		<span class="publicationdate">February 12, 2025</span>
	</div>
	<div class="copyrightstatement"/>
	<div class="toc">
		<ul class="nav-list">
			<li class="nav-item is-current-page" data-depth="1">
				<a newid="d3e90" class="nav-link" filepath="preface.html"
					href="#d3e90" entry-type="file">Evaluation</a>
			</li>
			<li class="nav-item" data-depth="1">
				<a newid="d3e139" class="nav-link"
					filepath="${release.notes.base}/preface.html" href="#d3e139"
					entry-type="URL">Release notes</a>
			</li>
			<li class="nav-item" data-depth="1">
				<a newid="d3e237" class="nav-link"
					filepath="../deployment-planning-guide/preface.html"
					href="#d3e237" entry-type="file">Deployment planning</a>
			</li>
			<li class="nav-item" data-depth="2">
				<a newid="d3e247" class="nav-link"
					filepath="../deployment-planning-guide/understanding-iam.html"
					href="#d3e247" entry-type="file">Identity and Access
					Management</a>
			</li>
			<li class="nav-item" data-depth="3">
				<a newid="d3e255" class="nav-link"
					filepath="../deployment-planning-guide/not-just-sso.html"
					href="#d3e255" entry-type="file">More than just single
					sign-on</a>
			</li>
		</ul>
	</div>
</nav>