Economy class baggage allowed for domestic plane

My wife and I are travelling in China with a US tour. The American airline to China allows us one carry on bag upto 6 kg and one checked bag upto 23 kg. We then travel in China on China Eastern. Our guide says the China allowance limits are total of two pieces: one carry on bag upto 5.0 kg and one checked bag upto 20 kg. China Eastern web site confirms carry on item weight of 5 kg but says checked bag may be up to 50 kg. We are confused and nervous about paying excess weight fee. Can anyone please advise us? Thank you in advance. Eric