I randomly checked an epub from Oxford University Press with the same academic subject as the one I'm working on and here’s how they do the chapter number/chapter title:
Code:
<h2 class="ch_title1" id="oso-666-chapter-1"><a id="page_1"/><a href="04_Contents1.xhtml#n0001">1</a></h2>
<h2 class="ch_title2"><a href="04_Contents1.xhtml#n0001"><em>Movie Title</em> Something</a></h2>
-------
h2.ch_title1 {
font-size: 160%;
font-weight: bold;
text-align: center;
text-indent: 0em;
margin-left: 0em;
margin-right: 0em;
margin-top: 2em;
margin-bottom: 0em;
}
h2.ch_title2 {
font-size: 140%;
font-weight: bold;
text-align: center;
text-indent: 0em;
margin-left: 0em;
margin-right: 0em;
margin-top: 0em;
margin-bottom: 2.75em;
}