Asset accounting -Unplanned depreciation

Hi friends,

I have asset , whose life span is 10 years...i have depreciation key LINR assigned to asset master , which wil calculate depreciation per period according to SLM method.

Now, i posted unplanned depreciation in year 2006 for some amount .but in hte year 2007 , the amount of depreciation/period posted as per SLM is same as it is before posting unplanned depreciation.

My doubt is why depreciation amount is not decreased/period in 2007 as we have posted additional amount as unplanned depreciation in 2006.

The system has reduced the net book value of asset but it hasn't decreased the depreciation posting per period. why?

Regards