Question about how interest charges on credit card

[Divaofsongs]

I thought if you paid your balance in full before the due date that you are not charged interest. Is that not how it works?

For instance, on my Capital One MC, I had a $322 balance due on Aug 5th with a statement date of Aug 8th. I made the full payment of $322 on Aug 2nd, three days before it was due and today when I logged on to check my account, the balance on my account was $4.06. I checked the transaction history and it is an interest charge. I thought they only charged interest if you don't PIF before the due date? I did have a balance of $215 post the previous month, is this charge for the balance that posted the previous month? Could someone explain to me how this all works because I am confused. 

[lhcole77]

It's called average daily balance method.

Here's a link that explains:

http://credit.about.com/od/creditcardbasics/qt/avgdailybalance.htm

[Divaofsongs]

Thank you, I am reading it now.