[Samba] Primary Group SID / RID weirdness

[Mi]

I don't quite understand the "Primary Group SID" numbers in my setup, 
especially the last part (which is the "RID", right?).

When doing a pdbedit -Lv, I notice that

- the first part is always the same, which seems normal. It's the domain 
part, right?

- the last number which I understand is the RID, doesn't seem consistent 
in my setup though:

* All machine accounts have 513 at the end, except one which has 1201.

* Most user accounts have 1201 at the end, except a few which have 513 
(and "nobody" has 514, administartor 3003).


I'm afraid there is something wrong with my setup, but don't understand 
it, and don't know what this might break.


This is a version "3.0.14a-Debian" PDC, with "passdb backend = tdbsam, 
guest"


Thank you for your help,

Mi