These days, it's generally agreed on that overall efficiency is at its greatest when the air wing is 50-60% of total carrying capacity. Aircraft require a lot of space for upkeep and maintenance in the hangar, and deck space is still more valuable. Clog that up too much, and things start going downhill.
This is why even though Liaoning can carry around 24 J-15s in the hangar and another 15 or so on the deck for a total of 39, she won't ever be carrying that much in any realistic scenario. An air wing of 20-25 aircraft is hence ideal, if going by the ratio. More could be carried if the J-15s weren't so darn big.