After finishing PAT, you get a 30 minute break (it used to be 15 but was recently changed). A timer pops up on your computer and starts counting down. You can choose to skip the break, or you can leave and do whatever you want (cell phone, view notes, eat, etc.). It is up to you to return to your computer in time because the test will start without you.
At my testing center they told me that I was not allowed to write down anything on the sheets during the tutorial/break times (no hole punching charts, no math equations, nothing!). But from what I've read on here, some testing centers don't care if you do. If you get lucky, then yes you can return from your break early to write things down.