Hi there, I need help, this is URGENT T_T.

I planed to go to Shenzhen and stayed there for 3 days so I applied "Single Entry" Chinese Visa. Now planed was changed, I will reach Shenzhen on Friday20 and will go to HK on Saturday21, come back to Shenzhen again on Sunday22 to take the flight bakc home. Is this possible???? Is a Single Entry Visa allow visitors to go out of China during the stay?? Please advise. Thank you in advance.