Wrong Calculation when to do depretiation calculation


i got some trouble with navision 2009 sp2,

when i am trying to do calculation depretiation entry for march

system result different amount with prior period

let say when feb depretiation calculation result 3000 (force day 30days)

when i am trying to do depretiation on march the system result different amount let say 2950 (force day 30days)

why? any suggestion?

if the result is exactly 2900 may be not problem for me because system counting 29days, but the system counting more than 29days but not 30days.

note : depretiation using straight line method



Need you depreciation book set up data to confirm this.

Also any additions (purchases) in period for that fixed asset.

Are you operating on months not periods?