Scorpion,
Just to keep it simple for you:
Assume that your CBA bank account balance was $153,392 as at the end of June.
Assume no transactions in July.
Then you find that at the start of August that account only shows $33,968 balance.
Would you get just slightly suspicious that something was amiss with the data and your money?
Its a bit hard to lose 119,424 between June and August without any July transactions!