Student in Beijing with a student visa and wants to visit Hongkong for 3 days but i have Single Entry

hi .. so i have a 6 months X issued here in Beijing because im studying here for a short course in Chinese language

but i want to visit HongKong during the Weekend but the thing is i only have single entry that was issued while im here extended from another student X.

now in my remarks. " permitted to stay until Feb ** 2014 for this time, and to stay for 30 days each time since the next entry.. let's say i can leave for hongkong but if i go back my 6 months X will be invalid anymore?