How would you like to order/sort the authors?

First read this getk2.org/documentation/tutorials/templating-with-k2-and-the-concepts-of-sub-templates to create your own override for that module in your Joomla template's html/ folder.

Then to sort by an author property (e.g. name or number of items), you need to usort() the $authors array in the authors.php override of the K2 Tools module. Example on how to sort a PHP array by one of its properties: stackoverflow.com/questions/3701855/how-do-i-sort-a-php-array-by-an-element-nested-inside

In your case, it's an array of objects.