I have X2 type, it's written down the visa is permitted to stay until 15 MAR 2016 for this time.

and to stay for 180 days each time since the next entry.
I have entered Only once with this type to china and I have ankother entry So Can I travel with the same X2 type after 15 MAR 2016? Or is it Two times Only BEFORE 15 MAR 2016?