The question relates to the number of characters displayed on the category index page. Here is a screenshot to illustrate the problem:
The last post subject is truncated to the first 20 characters. This value is hard-coded in Kunena but you can change the source by editing the file ../components/com_kunena/views/category/view.html.php at line 147:
if (!$content) $content = KunenaHtmlParser::parseText($category->getLastTopic()->subject, 20);
Change the "20" you see in this line to some other value. Remember, too, that you will need to make this change whenever you update Kunena in future.