If you pay off your credit cards in full on time each month, you may assume that your credit utilization is 0%. However, this is not the case. The amount owed figure is based on the amount the credit card issuer reports to each credit issuer. It is highly unlikely the issuer will send the data on the precise date when the balance is brought down to $0 by your payment.
Therefore, if you are trying to keep your credit utilization rate as low as possible, try not to max out your cards during the month even if you intend to pay the balance in full when you get the bill.