Dear Amalia Hasan ,
Please go to t-code: AS02 change asset master
under Depreciation Area tab: maintain Dep key, useful life, ord.dep start date, for
book depreciation:01
and save it.
i saw in screen shot it i showing Scrap values as required field
please change the field status for that asset/asset class to suppress/optional .
using screen lay out rules for assets.
hope this will help you
and also view the link
http://scn.sap.com/thread/1605300
Thanks
ssrao