Do I need a Transit visa for 23 hrs 50 minutes in Guangzhou?

I am planning to fly Kathmandu, Nepal via Guangzhou from Fukuoka, Japan. I checked the flight and found that the transit time in Guangzhou is 23 hrs 50 minutes. I also found that upto 24 hrs transit, the visa is not needed. I am worrying if the flight from Guangzhou delayed more that ten minitues it will cross the time limit. So, what will happen in this case?