Notify -- which servers get the request?

[Josh Higham]

I'm reading the DNS & Bind 3rd edition, and don't quite understand this bit
about how the notify request works:

'It determines which servers are the slaves ... by looking at the list of NS
records ... and taking out the one that points to the name server listed in
the first record specific field in the zone's SOA record ...'

That really confuses me.  What does the 'name server listed in the first
record specific ...' refer to?

My setup is this:

I have our 'main' server firewalled, and 4 slave servers that are the actual
nameservers in use, all slaved to the 'main' server which only transfers to
them.  If the NS records show:

ns.example.com
ns2.example.com
ns3.example.com
ns4.example.com

will ns.example.com get a notify request when the zone is updated?  I
believe that 2-4 will, but it looks like if the SOA is:

@    IN    SOA    ns.example.com. hostmaster.example.com.

then ns.example.com will not get the update.

Is this correct?  Will I have to specify 'also-notify' to force the notify
to go to ns.example.com?

Thanks,

Josh Higham