Diasonic Tech DMP-105 - Manual (Page 16)

Reference
In case of deleting the voice file - Index number on the set is arrayed sequentially
automatically.
While VOICE005.DMF is deleted on the V05 INDEX, it has been changed into
"VOICE 006.DMF".
Reference
At the record mode, folder cannot be created separately as at the
audio mode, and the recorded files are stored only at the "Voice"
folder.