At the top of each text type section it will describe the test format.  The flexible assessment allows you the option to record in audio or video format. You can re-record your responses before submitting and you are not being timed so you have more flexibility in the length of time you have to contemplate the question before responding.  You are also able to review the questions in advance.  The timed assessment is a more structured test.  For this test your flow is timed so you are only allotted a certain amount of time to think about your answer before responding and the response timing is automated so the recording will submit at the end of your time.  This test is also recorded in audio only.