BBL members in 4.05 and Invoice printing in 6.0.04

Hi
1st question:
We are using BPCS 4.05. I found that BBL file has a lot of members in names of 
workstations. Some of them have 1 or 2 records and others do not have any. All 
the orders that I entered, picked and confirmed are in the first member. So my 
question is when and why do those workstation-members get created and when do 
they get populated?

2nd question:
We have another department and they are using 6.0.04. There in the invoice 
printing program I see that a) when printing invoice it processes from BBH/BBL, 
b) when reprinting invoice it is using SIH/SIL. But there is another routine 
that processes from ECH/ECL. When is it used? In other words, my question is 
when does an  invoice get printed from ECH/ECL?


TIA
Amitava