Configuration Example:

service {
    upnp2 {
        acl {
            rule 1 {
                action allow
                external-port 1024-65535
                local-port 0-65535
                subnet 192.168.199.0/24
            }
            rule 2 {
                action allow
                external-port 1024-65535
                local-port 0-65535
                subnet 192.168.5.121/32
            }
            rule 3 {
                action deny
                external-port 1024-65535
                local-port 0-65535
                subnet 192.168.0.0/16
            }
        }
        listen-on eth1
        nat-pmp enable
        secure-mode enable
        wan eth0
    }
}

Looks like it is compatible with Synology DSM 7.