Successful deliveries 178%. Why?
It sounds like we have an overachiever here!

More seriously, I suspect that you may have found a bug in the count of recipients that occurs when you have the mailing set to email each contact, regardless of whether the email address duplicates another recipient of the mailing.

It wouldn't be surprising if practically all of the organizations had email addresses that were each actually the same as an individual's email address.  If you throw them all into one mailing (by your account and samuelsov's math), you'd have 5200 contacts.  Remove a few because they have no email, a few where the email is on hold, a few that have do not email, and a few that bounce, and voila--that's 4800 successful deliveries.

If that's the case, I suspect that the handy counter in CiviMail is simply assuming that you're using the CiviMail setting that suppresses repeat mailings to the same address per run.

You can confirm all this by clicking on the details in your mailing report and viewing the list of actual successful deliveries.  I suspect that you'll see both contacts and their organizations, many of whom have the same email addresses.