How does Tps relate to number of requests running?

I have a test set up where I have a fixed load generator (generating a fixed load of 1). But when I look at the statistics output in the table the Tps value fluctuates anywhere from 0.something to 4.something. The average response time is coming out at around 500ms which would suggest an average Tps of 2 (even though in this case none should be running concurrently) and 2 is what comes out in the Avg-Tps column. But the actual Tps column records varying values. Does this represent the actual threads that were kicked off in the last second? I guess it could be explained that way?