Computers depreciation question (life term)

Hi experts, 

I have one question regarding computer depreciation treatment in DPM table for compuer purchased in FY 2015-16. 

Computer have life of 3 years as per IT dept. Now how to calculate the cost to be charged in FY 17-18?

For example, computers are purchased in 2016 Jan, total cost is Rs 1,00,000. 

So in FY 2015-16 Depreciation booked is half rate of 60% due to 180 day rule. i.e Rs 30,000 

WDV on 1 April 2016 is Rs 70,000.

And Depreciation for FY 2016-17 is at full 60% = Rs 42,000 

Thus WDV on 1st April 2017 is 28,000 

Now life time is 3 year, so FY 2017-18 is the last year applicable, but now as per the rules only 40% is applicable. 

So Depreciation is Rs 11,200 and rest is not accounted and lost value. Is this method correct?