credit card grace period

I just came across the topic of credit card grace period, and could not find a consistent answer on exactly how it is supposed to apply in more complex situations than a monthly full payment.

On the back of the bill, it is defined thusly

We accrue periodic finance charges on a transaction, fee, or finance charge from the date it is added to your daily balance until payment in full is received on your account. However, we do not charge periodic finance charges on new purchases billed during a billing cycle if we receive both payment of your New Balance on your current statement by the date and time your payment is due and also payment of your New Balance on your previous statement by the date and time your payment was due.

This still is fairly ambiguous. In order to find out how this works exactly, to the cent, I did a simple test and found out.
(Read the article)