I tried again, selecting a 2 instead of 0 in the above values. To say it otherwise, everything is now set at 2. It changes nothing for the display.
Further down, css and html related code.
Spoiler:
div.img {
text-align: center;
text-indent: 0;
margin: 0;
padding: 0;
}
<div class="img">
<img alt="commandant Henry" style="max-width:75%" src="../Images/Image-02.jpg"/>
</div>
<p class="caption">Le commandant Henry</p>