Whether depreciation differs in companies act 2013

I bought machinery on 09 jan 2018  for 15000 , Depreciation rate as per companies act 2013 is 18.10% *1.5 = 27.15 % for 2 shifts .So depreciation upto 31st march 2018 will be 15000*27.15%*82/365 = 915. but if i calculate depreciation according to life of asset ( i.e. 15 years)  depreciation will be Rs.2.603  per day( (((15000*95%)/15)/365)  so depreciation for 82 days will be 320.14.. question arise why depreciation under both this situation differs. ?