If you want to know how much disc space is available then check it under info sheet..
You can record 15 mins back content by pressin record..
If you want to record time based use manual recordin feature..
Same movie record...two times, which one have low storage, you know only in HD+ box,,not in nxt hd, in nxt hd only having count in minute,second,,, not mb gb,,,if you want own movie library old box feature is best,,,
You can check Free Space Under Info Sheet which will give you info bout how much disc space is still left for you to record further.. Content always gets defined in hrs & minutes n seconds only as you are goin to play on NXT HD media player..
If you don't have enough space on Drive when you try to record, you will get notification that you don't enough space to record that session so that you can reduce the time of session and then record..