You probably have received a message leading you to your group usage statistics and a group management interface.
Among the files in your directory, you can find the following:
New files, since May 1st, 2017:
You can have one or more of these types of files.
The valid combinations are: commitment and legacy, premium and legacy. It is not possible to have premium and commitment at the same time.
These files are for people who have purchased shares/nodes with the old financing model. They contain information on Bellatrix and Deneb only.
Old files, until April 30th, 2017:
Invoices will be sent quarterly for the amounts in the following files: invoice, premium, commitment
The second link in the message you have received will take you to the list of users in your group. More information about the interface can be found here.
For the groups with Commitments it's possible to look at the live usage:
It shows an estimate of the current consumption as well as the expected usage based on the Commitment amount for the period it relates to.