In any conflict or potential conflict, the outcome is always calculated on the basis of numbers. This doesn't necessarily mean that you have equal your adversary, fighter for fighter, or tank for tank. Rather, it is an acceptable fleet, troop, squadron strength, which deems any conflict with their enemy, a stalemate. And there are many examples of this, where a country, though not as superior in numbers, has attained a level of strength by which it thwarts or hinders its rivals from open war.
We have witnessed such match-ups in the cold war, between United States and the Soviet Union. The same comparison can be made of Pakistan and hindustan, where hindustan has a superiority in numbers, however Pakistan has built up enough numbers to thwart or stemmed the enemy of thinking about open war. Also, the fact that Pakistan is Nuclear Power, prevents hindustan (wrongfully known as india), from declaring open war.
For China, open war with the America, is and should not be a possibility. Simply because both countries would perish in such a conflict. However, the key for China is, to achieve a respectable level of conventional military strength, which thwarts any aggressive designs by the enemy. As America is the only standing rival to China, it is only logical for China to attain a military strength which can challenge America and let it know, that open war, would cost it dearly.
Which is why, China should ideally achieve a respectable military strength, where America may have 11 Aircraft Carriers, China can do with a minimum of 6 Aircraft Carriers. And where USAF has a combined fleet of 2000-3000 fighter-jets, China should have at least 1700-2000. The same goes for the PLA, which needs more mobility, with the likes of larger Military Cargo aircraft and larger Military Cargo helicopters.
It isn't necessary for PLAAF to have 1200 J-10Bs, just because USAF has 1200 F-16s, rather a lesser number of J-10Bs, which are large enough to challenge America's air force's might. And even though, the manufacturing capability of reaching such strength levels in the PLA, PLAAF and PLAN/PLANAF, may take time, it is essential for China to achieve it and maintain parity with the United States.
A powerful China, is essential to the global balance of power, as it is foolish to allow just one power (United States) to rule the world. Balance is essential and imperative for a peaceful world.