Unnumbered priorities

Hi:
When should we use “unnumbered priorities”(n) in extensions.What is the different between these 2 forms of extensions.conf? and ,Are both true?
extensions.conf:
form1:
[Conferencerooms]
exten => 333,1,Answer
exten => 333,n,meetme(8000|cim)
exten => 333,n,playback(vm-goodbye)
exten => 333,n,hangup

form2:
[Conferencerooms]
exten => 333,1,Answer
exten => 333,2,meetme(8000|cim)
exten => 333,3,playback(vm-goodbye)
exten => 333,4,hangup

I’d appreciate any help.
Regards.

As far as I know, the ‘n’ was added so you could edit (as in add & remove lines) without having to re-number everything.