Depreciation calculation while having asset addition

[Sajee]

I have an asset with 12 months age, $1200 asset cost and calculating a depreciation based on the straight line method. Hence I'm getting $100 as depreciation per month. In month of August, an additional fittings happened in the asset and added a value of $300. 

I have two doubts here,

1. What will be the depreciation value of August.

2. What will be the depreciation value of August if I am considering, My Assets's age has increased from 12 months to 15 months.

Currently the system is calculating the previous months depreciation values based on the new added Asset Cost, while generating JV. But if the financial year is closed already, then there is no point in generating the past entries. How this scenario can be managed in the iDempiere?

Please correct if I'm sounding wrong.