The pricing plans are available here: https://cluelabs.com/pricing

On the Analytics line, you will see the number of xAPI statements you can process in a month.

You can track your current usage and your remaining credits on this page: https://cluelabs.com/account/usage

There is a default email notification that goes out when you exhaust 80% of the credits for the month, so this will give you enough time to make arrangements if needed. You can choose to upgrade to the next plan or do nothing. If you run out of credits, the xAPI statements will no longer be processed for the remainder of the billing period, and the credits will reset with the next billing cycle. You can verify that the 80% notification is turned on (or turn it off if needed) on the Account page.