[Dovecot] passwd, gid and uid

I forgot the answer for this: in 

http://wiki.dovecot.org/AuthDatabase/PasswdFile, we have the passwd file defined as

user:password:uid:gid:(gecos):home:(shell):extra_fields

What should the uid and gid be associated with? In my setup I told postfix to use Dovecot LDA's deliver, which then is saving files as uid:gid of 1500:1500. How would that affect the uid:gid used in the passwd file? From what I read in the dovecot's wiki, you want them *not* to be anything that has the rights to access the emails. So, does that mean any value for them will do?