I think it refers to about the same time periods. Also, there were a lot of slaves, and other non-citizens amongst the population. Here’s an article I just found with some information about the subject:
http://ccat.sas.upenn.edu/bmcr/2007/2007-04-59.html
This makes sense:
The second study, "The Size of the Athenian Citizen Population in the Fourth Century B.C.", is by far the longest in the volume, occupying some 42 pages total. In this work, as with the others in the volume, H. uses the so-called "shotgun method" of estimating ancient populations as he revisits the debate between those scholars who prefer a minimum of ca. 30,000 adult male citizens to those supporting a figure of ca. 20,000 in Athens in the fourth century.4 H. argues here in favor of the higher figure, basing his argument on the consideration of four main points: the total number of citizens required to operate the Council of Five Hundred; the number of Athenian ephebes; the number of citizens between 322 and 307 B.C.; and the Athenian importation of grain and carrying capacity of Attica.And I'll freely admit to not being in the least bit surprised that a journalist may have gotten the facts (10,000) in a story wrong!