Client ID change to invoice details

Unfortunately, my English is not good.

how do I get it out that the customer number is on the right side of the bill?


Customer number: 004

?? I just can’t get it out can someone help me?


<th data-ref="entity_details-client.id_number_label">Kundennummer</th>
>                <th data-ref="entity_details-client.id_number">$client.id_number</th

but unfortunately no customer number is displayed to me, why?


You may want to use $client.number instead