I created a custom post type and added post_tag and category as taxonomies for this custom post type. Now I created a few posts for this post_type, and added tags to it. When i go to the “edit_tags” page, the post count for the tag is zero. So I checked the database, and this is what I found.
wp_term_relationships shows that the tag is associated with four posts, all posts of the same custom post type.