ENTER BEFORE JAN 6TH 2015

i have multiple entry tourist visa. The PSB told me i can go to hong kong on the Jan 4th and come back on the 5th and i will be able to stay for 60 more days. After those 60 days are up my visa is expired and i must either get a new one or leave. Is this true? I don't trust them because they didn't know how to deal with a foreigner at the PSB i went to.