We will have 45 Mig-29K aircraft which are enough for both the carriers, though they can each carry upto 30 aircraft. Actually IN shouldn't be wasting more time for IAC-1, adding another 20 Mig-29K with updates such a AESA, new OLS would solve the problem for Vikrama and IAC-1 quite easily and at a much lower cost. Ordered today, they could begin deliveries as early as late 2020, early 2021. Total Mig-29K fleet of 65 is ideal with 30 split on each carrier and 5 as reserves.
Splitting 21 fighters on each Carrier for now (Vikrama & Vikra) allows for 42 which can be deployed while 3 are kept in reserve while more Mig-29s can be added. If IN can have a peace time availability of 16 to 18 aircraft out of 21 on the deck during deployments that's good enough. The Mig-29Ks especially when upgraded with AESA are more the capable enough to challenge all comers in IN's AOR.