PTR delegation 16 IPs

[Hen]

Hello,
i have all kinda problem with BIND 8.2-2 p5. All lookups work fine, but
the PTR.
My ISP even send me a template, i follow the exact rules but still can't
start named. I can however start named without the
224/28.141.36.208.in-addr.arpa. in named.conf. could someone please
point out my mistakes.and this is one of my error
Jan  7 20:49:17  named[69979]: master zone
"224/28.141.36.208.in-addr.arpa
" (IN) rejected due to errors (serial 12)
Thank you very much,
named.conf file
zone "224/28.141.36.208.in-addr.arpa" {
        type master;
        file "mydomain.rev";

};

zone "120/29.42.112.216.in-addr.arpa" {
        type master;
        also-notify {
        206.173.119.72;
        207.155.183.72;
        207.155.183.73;
        207.155.184.72;
        };
        file "cnc.rev";
};

ISP.rev file
$@ 120/29.42.112.216.in-addr.arpa.
@       IN      SOA     mydomain.org hostmaster.mydomain.org. (
                        12       ; Serial
                        86400    ; Refresh
                        600      ; Retry
                        2592000  ; Expire 30days
                        259200 ) ; Minimum TTL 3days

        IN      NS      nameserver.concentric.net.
        IN      NS      nameserver2.concentric.net.
        IN      NS      nameserver3.concentric.net.
        IN      NS      nameserver4.concentric.net.
mydomain.rev file
$@ 224/28.141.36.208.in-addr.arpa.
$TTL 43200
@        IN      SOA     mydomain.org hostmaster.mydomain.org. (
                       12       ; Serial
                        3600     ; Refresh
                        3600     ; Retry
                        60480    ; Expire
                        86400 )  ; Minimum TTL

        IN      NS      ns.mydomain.org.
        IN      NS      n2s.mydomain.org.

226     IN      PTR     ns.mydomain.org.
227     IN      PTR     n2s.mydomain.org.

TIA.