The volume set at startup is 5.
After booting, use the volume at 5 or higher, then turn off the car,
then start the car again, and when the device boots,
the volume will automatically adjust to the set volume of 5.
If you start the car and use the device at the automatically set volume level of 5 or lower
and then roboot the device, it will not return to the automatically set volume level of 5
but will start at the last used volume value.
There is no problem when the operating mode is sleep mode after turning of the ignition.
However, there is a problem only when the operating mode is in shutdown mode after turning off the ignition.
