From the question: Why did the people of 2149 evacuate to 85,000,000 B.C. particularly?, they discovered a fracture in time and space, which they were able to use to transport anything to 85 million years B.C. They didn't have their choice of destination time as
They were unable to CREATE a fracture in time and space on their own.
Then, how did they send people to several years later? For example, our heroes arrived in Terra Nova 7 years after Captain Taylor. How is this possible when the destination time wasn't under their control?