XP - How does it work?

[Tankdriver499]

I get that as a hitter, the more pitches you face, the more hits you do, your co goes up in the inning, but how does the pitching side go? It seems random to me. Sometimes a short inning is 191 so and others it is 265...what is the most so you can get pitching an inning?

So does someone have the exact formula on how game xp works?