The system will automatically run a script on the 1st of every calendar month. If the charge date is older than 30 days then the commissions will be moved to the available "Balance". Note that because this script runs on the 1st of every calendar month the previous month's subscriptions will not quite make the older than 30 days time period, it will always be missed. This is due to the logic design in the admin billing portal.
All accessible commissions are added to the available balance. Commissions will be put into a pending state to allow for credit card chargebacks, billing disputes, and post-paid billing.
Conclusion: "Balance" is payable/cashable commission that has been earned. "Pending Balance" is the commission that is waiting to be added to the available "Balance".