@ThinhDinh I use the <center> into the <th> or <td>, and I also can manipulate the font size, take a look in this exxemple below
<table style="width:100%; ">
<tr>
<th><center><h1>MEDIA</b> </th>
<th><center> # Classificações </b> </th>
<tr>
<td><center> de 5 </th>
<td></th>
</tr>

But you can also try
<th style="text-align: right"> setting to right or left if you need.