Assets net book value is negative and depreication is charged in Positive,

Hi,

For some assets in Assets explorere (AWO1N), net book value is showing as MINUS ( Negative Value ) and after that some time same assets started the depreciaion in Postive Amount with the same amount which the assets has the negative value.

I know the reason for the negative book value that our Book depreciation has settings in T.code-OBAN as the Negative value allowed and below zero is allowed.

I want to know, why the system starts the depreciation in Positive amount. What are settings for this. In Some of the assets that negative book value has adujsted in single period depreciation amount and in some assets it has been charged in multiple periods with equal amount.

Please could you tell me the reason of positive depreciation.,