Pledgeling tracks donations made through the API and charges your card on file (or pull funds via ACH) for all accrued donations on the earlier of 1) the day your accrued donations exceed your billing threshold amount, or 2) after 30 days have passed. All of the donations for the period are aggregated into a single charge. A new cycle then starts. 

Your billing threshold amount can be found on your Developer settings page. 

Even though the donations are charged to your payment method, for tax and accounting purposes they are considered to be individual donations by those donors and not a single donation by you.