This obvious because WordPress post has 6 columns normally and you have 13.
However, the problem is title bar is getting squeezed. In latest version the column widths are like this:
The Check box column: 2.2em ~ 3%
The Title column: flexible as its width is default(auto) (40% normally)
The Author column: 10%
The Categories column: 15%
The Tags column: 15%
The Comments column: 5.5em ~ 6.7%
The Date column: 10%
Solution
Add title width and specify a width but in em.
.column-title {
width: 15em;
}
Adjust this value to get desired look.
HOW TO APPLY
Use this code in your function.php
file or you can implement this in side a custom plugin.
Here we have a small style script, in case you have more styles to add to admin back-end then add it using a custom css file.
For small amount of script.
function adjust_admin_style() {
echo '<style>
.column-title {
width: 15em;
}
</style>';
}
add_action('admin_head', 'adjust_admin_style');
Implement styles in large scales
function prefix_admin_style() {
wp_enqueue_style('admin-styles', get_template_directory_uri().'/yourstyle.css');
}
add_action('admin_enqueue_scripts', 'prefix_admin_style');