That may not do what you think it does. Read the help file...
The Minimun volume setting does exactly that on my conventional TK-280. Off I can not hear the radio at all, at 22 it is honkin loud when I turn the radio on even with the volume as low as I can get it and still be turned on. As per the HELP file in my KPG-49D:
Minimum Volume Help
Selects the minimum volume level that will be automatically set each time the transceiver is turned ON.
Range:
Off(0) to 31 (steps of 1)
Default:
Off(Portable) / 8(Mobile)
< In Mobile transceivers >
Note 1:
After switching the transceiver OFF then ON, the newly selected volume level depends on the following relationships.
Note 2:
If the level previously selected using the VOL control is higher than the programmed minimum level, the VOL control level will be used.
Note 3:
If the level previously selected using the VOL control is lower than the programmed minimum level, the minimum level will be used.
kpg49d help