Rollback depreciation works in the same period ?

Hi

In R12.1.3 Asset added - 1000

Depreciation run -> depreciated done = 24

Create accounting done and posted to GL in May-13

Cost adjusted to 600

Depreciation run -> depreciated done = 14

Create accounting done and posted to GL in May-13

My depreciation of 24 should get adjusted , but it is posting both the amounts of 24 and 14

Any reasoning ?