The range can be given in any of the following formats:
 first X
 last X
You can also combine these with commas, eg "1-3, 4-7, 11, new" is a valid

The numbers of specific messages (eg, for the first two range types) can
be given in two forms, depending on the value of the player's "bbset" field.
If it is 0, all numbering is absolute. Messages are referred to by their
message id only, a value which does not change when messages are deleted
(so a message with id 2 still has id 2 when it is moved to the undelete 
queue). If it is greater than zero, that is taken as the size of the relative
set. Messages in the relative set can be referred to with a relative number;
the relative set covers the *last* messages on the queue. So, if your 
bbset field is 30, you can refer to the last 30 messages as 1,2,3,...etc
regardless of their message ids. 

Whether or not you use relative numbering you can use a \ to denote an
absolute id: "\2" is the message with message-id 2. 

The behavior of the current system can be simulated by setting the bbset
field to a very large number, like 1000.