Does anyone know in which order are the selectees called for interview? Do they go by case number or there are are more factors involved like the country of elegibility? Can anyone explain

FYI My boyfriend got an NL around April 20th, 2009 and he's in the US. His country of eligibility is from South America.
Thanks in advance for any replies!
Congrats to those that have received NLs and Good Luck to those that are still waiting
FYI My boyfriend got an NL around April 20th, 2009 and he's in the US. His country of eligibility is from South America.
Thanks in advance for any replies!
Congrats to those that have received NLs and Good Luck to those that are still waiting