I am German and holder of a double entry business visa for China.

Hi,
I would like to travel in the end of my business trip from Kunming to Hong Kong. Back I would like to fly from HK transit in Beijing and fly out to Germany, which is already booked. My stay in Hong Kong is 48 hs. Am I eligible for the 72 hours free transit?
Another question: I´m not allowed to stay longer than 90 days(tax issue). Does the 72 h count for my stay, or does the transit day count to the 90 days I spend with my M type?

Thanks,
Mia