# How to understand the calculation of interest for credit cards?

From Wikipedia

The general calculation formula most financial institutions use to determine the amount of interest to be charged is APR/100 x ADB/365 x number of days revolved. Take the annual percentage rate (APR) and divide by 100 then multiply to the amount of the average daily balance (ADB) divided by 365 and then take this total and multiply by the total number of days the amount revolved before payment was made on the account.

I think I understand the above, but wonder how to understand the below, especially the sentence in bold?

Financial institutions refer to interest charged back to the original time of the transaction and up to the time a payment was made, if not in full, as RRFC or residual retail finance charge. Thus after an amount has revolved and a payment has been made, the user of the card will still receive interest charges on their statement after paying the next statement in full (in fact the statement may only have a charge for interest that collected up until the date the full balance was paid, i.e. when the balance stopped revolving).

In the sentence in bold, why will the user "still receive interest charges after paying the next statement full"?

Thanks and regards!