sftp draft clarification

[Alok Aggarwal <Alok.Aggarwal%Sun.COM@localhost>]

Section 3 (General Packet Format) para 4 of draft-ietf-secsh-filexfer-01.txt
says:

"The maximum size of a packet is in practise determined by the client (the
maximum size of read or write requests that it sends, plus a few bytes of
packet overhead). All servers SHOULD support packets of at least 34000 bytes
(where the packet size refers to the full length, including the header above).
This should allow for reads and writes of at most 32768 bytes."

The header in question looks like this:

uint32			length
byte			type
byte[length - 1] 	data payload

How should the above para be interpreted? I'm a little confused with the part
that says all servers should support packets of *at least* 34000 bytes and then
says this should allow for reads and writes of *at most* 32768 bytes.

Also, why can't the server allow for reads and writes say ~64k bytes?

-Alok