How to modify child row table

Hi guys, how to change the design of the child row like here https://datatables.net/examples/api/row_details.html

Currently my code:

$(document).ready(function () {
    var emp = $('#countable').DataTable({
        responsive: true,
        order: [[ 2, "asc" ]]
    });

    emp.on('order.dt search.dt', function () {
        emp.column(1, {search:'applied', order:'applied'}).nodes().each(function (cell, i) {
            cell.innerHTML = i+1;
        });
    }).draw();
});

and table: