shortened the useful life of an asset

In PS 9.1 we are testing a scenario where a useful life of an asset is 60 months with the inservice date of 01/01/2012. After the Depr calc, the system is showing right depr values all the way up to 12/31/2016. Now we are changing the useful life to 18 months and were expecting the depr amount in the current month equal to remaining value(cost-accum depr) of the asset but instead it is showing 0.01 from august 2013 to Dec 2013.

When we run the same scenario by changing useful life to 30, system did the right adjustment to the depr amount from august 2013 onwards to Jun2014.

Thanks!