Set Specific proposal Invoice Number

Hi Everyone,

I’m using the following code to create my Invoices number

add_filter('wpo_wcpdf_format_document_number', 'wpo_wcpdf_custom_invoice_number', 10, 4);
function wpo_wcpdf_custom_invoice_number($formatted_number, $number, $document, $order)
{
    date_default_timezone_set("Europe/Berlin");
    $milisec = date('u');
    $lastdigit = substr($milisec, 0, 1);
    if ($document->type == 'invoice') {
        $formatted_number = date('ymd-Hi-s' . $lastdigit);
    }
    return $formatted_number;
}

How can I use something like that for the Proposal Invoices??