Value not send to 3rd-party

Hi,

I have linked CF7 to a online CRM. Everything is going well, but i have one problem with a value not being passed through. This is my debug information:

*** Service ***
Array
(
    [name] => my3rdparty
    [url] => http://www.example.com/process.php
    [forms] => Array
        (
            [0] => cf7_13
        )

    [success] =>
    [failure] =>
    [timeout] => 10
    [mapping] => Array
        (
            [0] => Array
                (
                    [lbl] => naam
                    [src] => naam
                    [3rd] => naam
                )

            [1] => Array
                (
                    [lbl] => email adres
                    [src] => email
                    [3rd] => email
                )

            [2] => Array
                (
                    [lbl] => onderwerp
                    [src] => onderwerp
                    [3rd] => onderwerp
                )

            [3] => Array
                (
                    [lbl] => productnummer
                    [src] => productnummer
                    [3rd] => productnummer
                )

            [4] => Array
                (
                    [lbl] => aantalproducten
                    [src] => aantalproducten
                    [3rd] => aantalproducten
                )

            [5] => Array
                (
                    [lbl] => relatietype
                    [src] => relatietype
                    [3rd] => relatietype
                )

            [6] => Array
                (
                    [lbl] => omschrijving
                    [src] => omschrijving
                    [3rd] => omschrijving
                )

        )

    [separator] => ,
)

*** Post (Form) ***
http://www.example.com/process.php
Array
(
    [_wpcf7] => 13
    [_wpcf7_version] => 4.1.1
    [_wpcf7_locale] => nl_NL
    [_wpcf7_unit_tag] => wpcf7-f13-p121-o1
    [_wpnonce] => 0c16a5e165
    [relatietype] => COMPANY
    [naam] => John Smith
    [email] => example@example.com
    [onderwerp] => TEST
    [productnummer] => 803580
    [aantalproducten] => 1
    [omschrijving] => This is a test message...
    [_wpcf7_is_ajax_call] => 1
)

*** Post (to Service) ***
Array
(
    [timeout] => 10
    [body] => Array
        (
            [naam] => John Smith
            [email] => example@example.com
            [onderwerp] => TEST
            [productnummer] => 803580
            [relatietype] => COMPANY
            [omschrijving] => This is a test message...
        )

)

*** Response ***
Array
(
    [headers] => Array
        (
            [date] => Tue, 07 Apr 2015 10:29:58 GMT

            [server] => Apache/2.2.29 (Unix) mod_ssl/2.2.29 OpenSSL/1.0.1e-fips DAV/2 PHP/5.4.35
            [x-powered-by] => PHP/5.4.35
            [vary] => Accept-Encoding,User-Agent
            [content-encoding] => gzip
            [content-length] => 25
            [connection] => close
            [content-type] => text/html
        )

    [body] => <pre>
    [response] => Array
        (
            [code] => 200
            [message] => OK
        )

    [cookies] => Array
        (
        )

    [filename] =>
)

The value of 'aantalproducten' which means the amount of products is not send to the processing file. Any idea how to solve this?

https://wordpress.org/plugins/forms-3rdparty-integration/