The VS-1680 allows you to clear the existing markers to free up the locations for a new ones.
Please follow these steps to clear an existing locator memory:
1) Hold CLEAR
2) Press Locator button you want to clear

Now you can use this Locator button to mark a new time.
6-1. If a CD-RW disc,which contains data is placed in the CD-R Drive in step 1, "Erase?" appears in the display.
6-2. If you erase the existing data, press [YES]. "Erase Disc" appears and all the data in the CD-RW disc is erased. If you do not wish to erase the data, press [NO].
6-3. When erase is finished, "Can't be played back with Audio CD player" appears in the display. This is to warn that common audio CD players cannot play back a CD-RW disc. Press [YES]. Or press [NO] to go back to the step 3.