I think the "small" amount of airplanes it can carry is due to several factors. The large size of the J-15, the extra footprint required to carry fuel oil tanks because it is not nuclear powered, possibly issues with internal layout not being optimized. Still I think it is premature to consider those numbers. AFAIK we don't know the real capabilities of the Type 001A. They are extrapolated from the Kuznetsov and may not be accurate at all since this is the first carrier fully built in China which has had some design changes.