The NNTP "Group" command tells me the TOP article number.

You (DFS) replied ( to me ):

Instead of relying on article numbers,
my newsreader remembers the last 10 Message-ID's.

 
If you don't use article number,
how do you know you've downloaded the last 200 cola posts ?

The NNTP "Group" command tells me the TOP article number.
Using a Message-ID "BookMark", I get the LOW article number.

I repeatedly request up to 100 articles at a time
via a block of 100 NNTP commands
( because one may NOT specify a range, from LOW to TOP ).