Billing stats includes:

Scheduled, Collected, Pending, Expected, and Past Due values.

Scheduled value is the sum of all Autocollect payments due during the current time period. This amount can change based on memberships entered, and memberships cancelled.
Collected value is the sum of all Autocollect payments processed including credit cards and echecks for the current time period.
Pending value is the sum of all Autocollect Echecks that have been processed but not currently approved/declined for the current time period.
Expected value is the sum of all Autocollect payments due for the current time period that have not been processed yet.
Past Due value is the sum of all Autocollect payments that are 1 day or greater past due.