From Books of prime entry to Nominal Ledger

Hello Fellows,

    I am getting ready for C02 and there is something easy at first glance but bothers me a lot. It is in relation of prime books and their postings to nominal ledgers and the effect on the trial balance in case of error. One example is overcasting of the total column of cash payments, why this affects the trial balance? In my view.....if the total of the cash payments in the cash book is wrong it will go wrong equally in the Cash Account and Expense Accounts in the Nominal Ledger.

    This specific example I see it in some exercise and it is said that this overcasting will affect TB and suspense account would be needed.

    Another example is cash book column related to drawings has been overacted. It is said again that will affect TB and posting on suspense account would be needed. This I also do not understand.

Thanks

BobSun