Closing balance of july ending and opening balance of August 1at is differs on dimension statement

Hi Experts

question in ax 2009

I try to run the dimension statement (GL-Reprots-Dimension Statement) for the month of july 1st to july 31st .

Parameters I entered as trasactions= ledger

Main focus= department. from date - 07/01/2011 to date as 07/31/2011

specification positng and posting layer as current.

under Range ledger transactions-ledger account = mentioned one account

Depeartment = 300

click ok

the ending balance of july is 300,000

now i ran the same account for the month of august 1st to august 31st

the opening balance is 432 987

why is not the opening balance is not same as closing balance of the previous month.

Thanks

sk

I would like to run a report Dimension basis as a focus,is there any other report other than dimension statement