In this competition we are talking about sampling from the environment; you can use as many of the human samples as many times as you want.
The motivation is this: it is far more feasible to collect a bunch of humans driving cars than to run \epsilon-greedy random exploration for some RL algorithm with a real car. Hence we limit the number of samples you get with the real car to 8,000,000, and encourage you to use the dataset as much as possible.
Hope this helps!