Meaning of fields in named_dump.db

[blrmaani]

All,
  I was looking at the named_dump.db file and didn't understand the
meaning of several fields.

1. [v4 TTL 7] [v4 success] [v6 unexpected] [v4 not_found] [v6 nxrrset]
[ttl 1777] [flags 00000000] [srtt 333]

What exactly are these?

I know that the IPs with lower srtts are preferred but I don't know
what is not_found or unexpected mean?

Also what is the difference b/w lowercase ttl (ttl) and uppercase ttl
(TTL) in the fields above ?

thanks in advance
maani