That's an extremely high number I'd actually believe. Also I read there's a process for getting a record certified. It's something like the record company has to pay $500 to check the shipment numbers and then another $500 to have the Gold/Platinum record made. That's probably why Testament...
I've heard they were bigger in those areas (Especially Germany). The fact that their record label was lazy and never gave Certifications to bands like them and Testament doesn't exactly help either. If they did then it could give us a good idea on how well they did sales wise.
I still think it'll do well. According to Jeff Waters of Annihilator, Testament (as well as Overkill, Exodus, Kreator, and Destruction) have been having their biggest record sales in over 15 years...