I have a question about the multiple entry L visas

Multi-Entry Visa with 6-month Validity 600,000 1,200,000 600,000

Multi-Entry Visa with 12-month Validity 900,000 1,200,000 900,000

As we are planing to be traveling in and out of China, we want to know if either the 6 month or 12 month visas allow you to stay in China for more than 30 days at one time and how many times can you come and go from China with these Visas. My husband and I are both American and our adopted son is Indonesian.