Carplay Volume

[Wxman]

I will probably mention this to dealer next time in, but looking for any insight.  When using Apple Carplay (iPhone SE) in my 2017 LT I am not able to adjust the volume for the map directions, phone call audio, etc.  with either the steering wheel controls or the head unit knob.  When I attempt to change the volume during a call or during directions the 'volume bar' appears in red, but the volume doesn't change.  Also, if the radio audio is off, it comes on.  It doesn't appear to me that anything else is happening.
This is not how it works in my '16 Malibu.  I can set separate volumes for audio, calls, map directions.  It is a little more upscale than the LT, but it seems to me the truck should act the same.

Any insight??

Thank you

[Wxman]

Update.  This is what I have found.  Steering wheel volume controls and volume knob will adjust Siri/map direction volume.  The red I was seeing is some kind of minimum that the volume controls will not go below.  I can set different radio and Siri/map volumes.  I just cannot go below this minimum volume.  Phone controls don't seem to affect volume during carplay use.  I also played around with the volume settings in the map app and they do not seem to affect the volume or this minimum volume when using carplay.
My Malibu does in fact operate the same way.  For some reason this minimum setting in the Malibu is lower to my ears and I guess I have been making any adjustments above it.  The volume does adjust and I never noticed the minimum because I was using settings above it.  The Silverado minimum is louder to my ears and I was attempting to use settings below it and did not get anywhere.
This is all I could figure out.  If anyone knows a way to lower this minimum, red bar Siri/map volume I would love to try it.