I recently went to China and the Visa that I received has an "M" beside "Entries."

Duration of each stay is 60 days and it expires in 10 years. Does this mean that I can enter as many times as I want to in the next ten years as long as I don't stay more than 60 days? I only applied for a single entry one, but it came back with an "M." I asked immigration at the Beijing airport if it was multiple entry and he nodded, but I'm not sure he understood my question