Reverse records in /22 network

[Cuttler, Brian (HEALTH)]

I have dynamic dhcp and DNS in production now, but think that I may have left something out.

Machines register in DHCP, and I see A and PTR records appear in DNS.

However, I'm using a /22 address space, 10.57.36-39.0 and I only declared a single pointer database 

Zone "36.57.10.in-addr.arpa." in {
Type slave;
Masters {xx.xx.xx.xx};
File "db.esp122-ptr";
};

And I now wonder if I don't also need tables for 37.57.10.in-addr.arpa and 38 and 39 as well. And then how to properly declare in dhcpd.conf.

Thanks for your help, not easy to google this question...

Brian