Last week, during its first quarterly earnings report as a public company, Facebook. In the social-networking giant's 10-Q filing published last night, the company disclosed that nearly 20 percent of the latter number,, accessed the social network in June solely from their mobile device.

So, how many of these accounts are fake? Facebook estimates 8.7 percent, or 83.09 million accounts.

That's a huge jump, both in raw numbers and as a percentage, from Facebook's last estimate. Back in March, Facebook said 5 to 6 percent of accounts are false or duplicate. At the time, this meant between 42.25 million and 50.70 million users.

Does this mean that a huge amount of fake accounts were created over the last five months? Not really: Facebook is simply being more transparent when it comes to specifying which false accounts it is tracking. Before it only listed duplicate and false users, and now Facebook has broken down the latter number further: duplicate accounts (4.8 percent), user-misclassified accounts (2.4 percent), and undesirable accounts (1.5 percent).

Here are the official details. First, the usual legalese warning:

The numbers of our MAUs and DAUs and ARPU are calculated using internal company data based on the activity of user accounts. While these numbers are based on what we believe to be reasonable estimates of our user base for the applicable period of measurement, there are inherent challenges in measuring usage of our products across large online and mobile populations around the world. For example, there may be individuals who maintain one or more Facebook accounts in violation of our terms of service, despite our efforts to detect and suppress such behavior.

Now for the goods:

We estimate that "duplicate" accounts (an account that a user maintains in addition to his or her principal account) may have represented approximately 4.8 percent of our worldwide MAUs as of June 30, 2012. We also seek to identify "false" accounts, which we divide into two categories: (1) user-misclassified accounts, where users have created personal profiles for a business, organization, or non-human entity such as a pet (such entities are permitted on Facebook using a Page rather than a personal profile under our terms of service); and (2) undesirable accounts, which represent user profiles that we determine are intended to be used for purposes that violate our terms of service, such as spamming. As of June 30, 2012, we estimate user-misclassified accounts may have represented approximately 2.4 percent of our worldwide MAUs and undesirable accounts may have represented approximately 1.5 percent of our worldwide MAUs.

It's worth noting that an active Facebook user does not necessarily mean someone using Facebook.com. The metric refers to using your Facebook account somewhere on the Internet. Still, Facebook is pretty good at reporting its number of active users, at least compared to other companies that purposefully bloat their numbers with inactive accounts.

Either way, the new numbers follow two very different stories this week about the Facebook platform. The first argued that there are just too many bots for Facebook Ads to work while the other explained how Facebook Ads can be used to sell products to real users.