Wordpress get Ajax response for total post per page

Question

Aim

The total to be equal to the amount of post within the selected category or sub category.

What im getting

I am getting 0 when trying to get the number of post available in a category.

I have tried (code bellow), however I keep getting the response 0 for total

Summarey

So I have a custom post type custom_post and I am trying to get the number of post in a selected the category / subcategory selected (using standard category and sub category type taxonomy)

I am using the category / sub-category ID.

My ajax

<?php // the ajax function
add_action('wp_ajax_filterPosts', 'filterPosts');
add_action('wp_ajax_nopriv_filterPosts', 'filterPosts');

function filterPosts()
{
    $response = [
        'posts' => "",
    ];
    
    $all_args = array(
        'posts_per_page' => -1, // returns all posts
        'post_status' => 'publish',
    );
    
    $filter_args = array(
        'post_status' => 'publish',
    );
    
     if ($_POST['limit']) {
        $filter_args['posts_per_page'] = max (0, (int) $_POST['limit']);
    }
    
    if (isset($_POST['offset'])) {                      
        $filter_args['offset'] = max (0, (int)$_POST['offset']);
    }

     if ($_POST['post_type_js']) {
        $filter_args['post_type'] = $_POST['post_type_js'];
    }

    if ($_POST['category']) {
        $filter_args['cat'] = $_POST['category'];
        
        // Get the total number of posts for the category
        $all_args['total'] = $_POST['total'];

    }

    $filter_query = new WP_Query($filter_args);

    $all_query = new WP_Query($all_args);

    

    if ($filter_query->have_posts()) :
        while ($filter_query->have_posts()) : $filter_query->the_post();
            $response['posts'] .= load_template_part('/template-parts/posts-filter/single-post');
        endwhile;
        wp_reset_postdata();
    endif;

    echo json_encode($response);
    die();
}

My javascript

Alpine.data("filterPosts", (adminURL) => ({
    posts: "",
    limit: 6,
    total: null,
    category: null,
    post_type_js: post_id,
    showDefault: true,
    showFiltered: false,
    offset: 0,
    
        filterPosts(id) {
        this.showDefault = false;
        this.showFiltered = true;
        this.category = id;
        this.offset = 0; // <-- reset offset to zero
        this.total = 0;
        this.fetchPosts();
    },
    
    loadMore() {
        this.loadingMore = true;
        this.total = null;
        this.offset += 6;
        this.showFiltered = true;
        this.fetchPosts(true);
    },

    fetchPosts(append = false) {
        var formData = new FormData();
        formData.append("action", "filterPosts");
        formData.append("limit", this.limit);
        formData.append("post_type_js", this.post_type_js);
        formData.append("offset", this.offset); 

        if (this.category) {
            formData.append("category", this.category);
            formData.append("total", this.total);
        }

    fetch(adminURL, {
        method: "POST",
        body: formData,
    })
    .then((res) => res.json())
    .then((res) => {
            if (append) {
                // Appends posts to the end of existing posts data
                this.posts = this.posts.concat(res.posts);
            } else {
                // Resets the posts data with new data
                this.posts = res.posts;
            }

            this.loading = false;
        });
    },
    
    getTotal() {
    var formData = new FormData();
    formData.append("action", "filterPosts");

    fetch(adminURL, {
        method: "POST",
        body: formData,
    })
    .then((res) => res.json())
    .then((res) => {
        this.total = res.total;
    });
},

init() {
    this.getTotal(

Response in console

action: filterPosts
limit: 6
post_type_js: custom_post
offset: 6
category: 1094
total: 0