Gah! What a messy convert.
(I say this, just from looking at the Calibre numbers assigned.)
<body class="calibre5">
<div class="calibre6">
<h1 class="calibre11" id="calibre_pb_21"><span class="calibre12">ten</span></h1>
<div class="calibre13"></div>
<p class="calibre10"></p>
You did not show The baisic body CSS (calibre5)
Then there is the Div (calibre6)
Then there is the Heading (calibre11
calibre12) that appear to do the same things
differently
then there is the div (calibre13) which may have been a HR ar some time (it has a small height value consistent with line thickness)
You have Line heights (I rarely use them except in mixed font size cases), margins, empty (no text/image) div's and p's