Part of the process is to unify targets across communications mechanisms. That number would very likely mean distinct "individuals," although it could include people using multiple accounts that had not yet been associated with the same person/group.
It's easier when you can associate IP addresses with multiple accounts, of course, but there are a lot of traits (and I'm sure NSA has more than I am aware of) that can be used as similarity metrics to create a probabilistic hierarchy of account agglomeration.
Throwing clique analysis into the mix, which is of course where the most important analysis goes, also helps establish the probability that multiple accounts may be controlled by one person.
It's easier when you can associate IP addresses with multiple accounts, of course, but there are a lot of traits (and I'm sure NSA has more than I am aware of) that can be used as similarity metrics to create a probabilistic hierarchy of account agglomeration.
Throwing clique analysis into the mix, which is of course where the most important analysis goes, also helps establish the probability that multiple accounts may be controlled by one person.