Did not find from where does the eConnect consider the LOCNCODE – Location Code

I am trying to integrate Sales Transaction entry (Invoice) through eConnect and everything is working fine except when I am not passing any value for LOCNCODE in Header. The invoice data are successfully integrated into GP, when I open the sales transaction entry window in GP I see that there is a value for LOCNCODE in header section which I have not passed during integration. 

So, I was wondering from where eConnect pulls the value for LOCNCODE as I checked for the same in Customer Maintenance window but the value of LOCNCODE do not match.

Can anyone here tell me from where eConnect pulls the value for LOCNCODE?

Thanks,
Amelie