How much is the daily rate for storing luggage at the Left Luggage Office at Kunming Airport?

So I will be travelling with a family of 4 and will be most likely storing 7 or 8 luggage bags at the Left Luggage Office in the airport. I would like to know what is the current daily rate for the baggage and also is there a size requirement for the bags? What are the timings for the office as I will be arriving at around midnight at the airport and then picking up the bags at around 9 pm the next day? Thanks