How to customize the display of a block?
You can customize the display of a block by using Block Class module.


  Block Class allows users to add classes to any block through the
  block's configuration interface. By adding a very short snippet of PHP
  to a theme's block.tpl.php file, classes can be added to the parent
   element of a block. Hooray for more powerful
  block theming!



In this case, first look at the CSS selector and then add a single line to theme's CSS file such as:

.label { display: inline }



It's about CSS.