Where does this field get its value?

I’ve inherited maintenance of a wordpress site with a custom template. I’m trying to change the value of a phone number that is displayed throughout the site. I’ve found the field by looking in the template php files here: <a href=”tel:<?php the_field(‘phone_number’, ‘option’); ?>”><strong>Phone:</strong> <?php the_field(‘phone_number’, ‘option’); ?></a> I tried editing the page to see…