It is easy to conduct simple home experiments, or even do them as thought experiments to determine the answer to this question.
Think of a child's balloon. Inflate the balloon with air whilst holding the neck of the balloon with your fingers:
Now relax the pressure on the neck of the balloon very slightly. You will find that the air leaks out of the balloon very slowly. It does not all escape instantly. It takes time. This is because the molecules of gas (air) cannot all move through the exit at the same time. They have to move towards it before they can exit. A bit like people rushing through an exit:
The same is true for a space vehicle. With a small exit the air molecules will take time to pass through the very small hole. If the hole is small enough the lost air can be replaced. However, if the whole is large enough the the air will escape more rapidly: