Project Fi is giving customers free extra credits due to lag that it experienced in data reporting. If you're a Fi subscriber, chances are that over the last couple of days you received an email from the carrier alerting you to a lag in the reporting it had which resulted in unintended data usage for that period. According to the email as well as a post from a Project Fi team member on the Project Fi Help Forums, the lag in reporting for customer data usage resulted in some of the data during the billing period of June 14th to July 14th not being counted on that period's bill. This in turn will be causing the data to show up on the following period, so to offset things customers are getting free credits that will basically nullify that extra data use.
Both the help forums and the email state that the extra credits should appear in the "next couple of days" and will be visible under the extras section. The extras section can be found right on the home screen of the app and is where you'll also find things like the Fi Protection plan, which is basically insurance for your phone.
If you aren't currently seeing these extra credits on your account yet, not to worry, as the post on the forum is from Friday and the emails (such as the one that was received below) went out 3 days ago as well which means it was sent out heading into the weekend. It's likely that due to the weekend the credits weren't applied yet, and may take another day or two to show up. Of course, there is no way to verify this but users who don't see the credits showing up as designated in the email simply need to keep an eye out for them as they should appear soon. As pointed out by one user on the Project Fi Help forums, this is an unusual practice in the wireless industry, which is perhaps one more reason to love Project Fi. In addition to showing up under the extra section in the Project Fi application, the extra credits will also show up on the next upcoming billing statement.