The only part you can have control over is yourself.
Try it.
Re-read the instructions, get the last snack when you can, read whether you can drink some water, make sure you will be there on time and make sure you will be ready for the surgery when your timeslot comes.
It would be a shame if you got cancelled because of some overlooking on your side.
The list construction is something you can't control, because it would mean giving you a lots of information about organisation, medical knowledge and other patients private health information, so it just isn't practical.
Every information from this thread is just an anecdotal evidence and has limited applicability. The list construction works differently in different types of hospitals. You are booked into the morning session, so 6pm is really really unlikely. People suggested you might go last before you added the morning session detail, so don't worry about that too much.