Adding theme strings to .PO file

I'm trying to translate some strings in a WP theme I'm using, but apparently there are some differences in the PHP code. Here's an example:

<?php
echo apply_filters( 'jobboard_job_posted_text', _n( 'Job Posted', 'Jobs Posted', $job['jobs']->publish, 'jobboard' ) );
?>

I've used POEdit to create a new catalog, update it from source code, I've added _n in the keywords, but when I uploaded the compiled .MO file, the strings remain untranslated on the website.

Could anyone help me figure out how do translate these lines?

Thank you!