General John R. Allen. (AP)

When stories move quickly, a single detail can sometimes take on a life of its own. The day's developments surrounding CIA Director David Petraeus includes one such detail: the number of e-mails that General John R. Allen is said to have sent to Tampa socialite Jill Kelley.

A defense official originally stated that the e-mails, sent since about 2010, numbered 20,000 to 30,000. It was quickly reported that this number in fact refers to the number of printed pages of correspondence, which actually number "a few hundred," Craig Whitlock and Rajiv Chandrasekaran reported in today's Post.

Allen and Kelley, who threw parties and other social events involving senior leaders at the Central Command, did exchange “a few hundred e-mails over a couple of years,” beginning when Allen was the deputy commander at the Central Command, this senior official said. But “most of them were about routine stuff.”

“He’s never been alone with her,” the senior official said. “Did he have an affair? No.”

The senior official also emphasized that the volume of communications between the two “was nowhere near” 20,000 to 30,000 personal messages. The official said the high page count reported by the FBI may have been the result of printing numerous individual messages that contained lengthy threads of earlier exchanges.

If 20,000 to 30,000 still seems like a lot of pages, consider that investigators likely reprinted entire threads every time a new message was added, and that the rigorous requirements for legal document discovery often entail repetitions, onerous formatting restrictions, and exhaustive inclusiveness. As Reuters reporter Erin Smith tweeted, "Clearly anyone who thinks that 30,000 documents = 30,000 substantive/non-duplicative documents has never suffered through a doc review."

And yet it seems that "20,000 to 30,000" figure is just too good to die, persisting in social media, repeated in blogs and commentary, and doubtless in much dinner chatter across at least Washington, D.C., tonight. If it comes up, you'll know the real number – according to the most recent reports, at least.