the ones doing less than 18 hours.

I do 18 teaching hours /week, @ 40 minutes/ teaching hour. That equals 12 clock hours. We should warn newbies that they can be duped by wily Chinese employers. If the contract offered states 'hours', that will mean clock hours, whereas if it states 'teaching hours', it'll mean teaching periods. But if it says 'hours of teaching', it also means clock hours (= sixty-minute hours). I wouldn't take any teaching post in China that requires me to teach 18 hours/week! I value my spare time very much!