"Total Amount Due" is the sum of "Balance" and "Current Charges", which is the amount to be settled this month. Any odd cents will be carried forward to your next bill.
Example: "Balance $10.22" + "Current Charges $153.97" = $164.19. The "Odd Cents" of $0.19 is carried forward to next bill. Hence, the "Total Amount Due" = $164.00.
If "Total Amount Due" displays "CR" it means that there is no payable amount for this bill.