How did the US arrive at a precise figure of 53,670 jobs claimed to be supported by the recent trade deals?

Obama's contingent has signed business deals in India, notably the purchase of aircraft from Boeing and turbines from GE. It is claimed that these deals support 53,670 jobs, if not create new ones. I mean, Boeing and GE already are huge companies with a million plus workforce. How was this figure of 53,670 arrived at? If the deals were about greenfield investments, it makes sense. But in this case??