Visa to China on technical support setting up factory

You don't need a work visa, you need a 1 year multiple entry F visa with 60 days stay duration per entry, now your visa permits you to stay in China for 30 days per entry, you have to exit Mainland China, to go to Hong Kong or Macau, then return to Mainland China for another 30 days stay duration, it is not a good advise to apply for visa extension at the local Public Security Bureau, once you get a extension, you will lose you multiple entry. There is no total limit day to stay in China for 1 year.