This option on the Detail View page lets you
see how much has already been recorded on rewritable media (such as your
CD-RW or MiniDisc music mixes). Now you can know which still have
enough space left! This option will calculate the timing and number
of tracks for each of the media labels and directories, and show them sorted
in order of most space left.
Any entries shown in red indicate that
at least one album on the target media had no track timing, so 3 minutes
per track (plus inter-track gap of 2 seconds) has been used as an estimate,
which of course could be way off so such target media's actual remaining
space should be checked before recording.