Could treat the 3 billion figure as the "official" number of people sent there with the actual one being considerably lower due to a combination of factors. One can imagine having that many people transfered there that quickly makes it difficult to keep track of them properly, many could have died or left for greener pastures, many might not have even arived in the first place. A lot can happen behind the fog of war, especially if people put some effort into hiding it.
