Magnavox ZV457MG9 Owner's Manual page 72

You can delete titles which you do not need anymore.
Please be advised that the titles once deleted cannot be
brought back to the disc.
For DVD+RW/DVD-RW, when the last recorded title in the
title list is deleted, the available disc space to record on
will be increased. For DVD+R/DVD-R, the disc space to
record on will not be changed.
3
Use [A /I'] to select "Edit", then
_ress [OK].
4
Use [A /V] to select "Title Delete",
then press [OK].
1
2
Press [DVD] first.
Press [TITLE].
Use [A / V] to select a desired title,
then press [OK].
Use [A / V] to select "Yes", then press
[OK].
After that, "Are you sure?" will appear, select
"Yes" and then press [OK].
Title will be deleted.
Data will be written onto the disc momentarily.
e.g.) DVD+R/DVD-RW/-R
After editing is complete, the title list will appear.
e.g.) DVD+RW/DVD-RW
70 EN