How to display data about updating the number of images in a Wordpress post?

Question

Gallery

Good day.
I wanted to indicate the number of pictures in the post.
used for this

$num_attachments = array_sum ( (array) wp_count_attachments('image') );

Can you please tell me how to update?
For example post: City of Krasnodar - (total 49 photos)
And after the update: City of Krasnodar - 15 photos added (total 64 photos)