Hi Seasoned Traveller,
Open seated dining is a more flexible way of dining. It is similar to restaurant-style seating where, for example, you can ask for a table of two. You can dine alone or choose to be seated with other guests. Also, you are not given a set time in which to be seated, instead a slot of a couple of hours - so timing is very flexible.
I hope this helps.
Kindest Regards,
Monty