Считаем кол-во выведенных товаров на странице - mFilter2

catalog.tpl

    <div class="mt-textbox">
        <p>Showing  
        <strong id="START">{$_modx->getPlaceholder('mse2_start_page')}</strong> – 
        <strong id="END">{$_modx->getPlaceholder('mf_limit')}</strong> of  
        <strong>{$_modx->getPlaceholder('mf_total')}</strong> results</p>
    </div>
    
    <script>
        $(document).on('mse2_load', function(e, data) {
            let page = data.data.page;
            let start = page * 9;
            let end = page * 9 + 9;
            $('#START').html(start);
            $('#END').html(end);
            console.log(e, data);
        });
    </script>