What do you mean by unique, available titles?

You need plenty of unique and available DVDs in your rentals in order to ensure you always get sent a DVD as soon as possible. That means:

• Unique - not part of the same set.
  Some titles will include more than 1 DVD - for example a TV series title might have six DVDs in it. We count this as a single title as we can only send the first or next disc of a series to you before any of the others (assuming it is selected to be sent in series order). So for example if you had two titles with 6 discs in each in your rentals, that would only count as two unique titles - if all the copies of both were out on loan to other customers, then we wouldn't be able to send the next disc in the series to you.
• Available - released on DVD.
  You can find upcoming release DVDs on our site and can add them to your rentals - however as they have not been released they are not 'available', and we obviously can't send them out to you. Therefore you need plenty of available DVDs to ensure we can send you something.

We recommend you keep lots of unique and available titles in your rentals, ideally 2 or 3 times the number of credits you have. This will help to ensure we can always send you something straight away.