I can't stream compressed above 192kbps

[grant420]

I'd like to stream compressed audio at 320 kbps but despite using these two transcoding options:

ffmpeg -i %s -map 0:0 -b:a %b320 -v 0 -f mp3 -
and
ffmpeg -i %s -map 0:0 -b:a %bk -v 0 -f mp3 -

configuring iSub app on my iPhone7 to allow up to 320kbps when playing over cellular (max over wifi, of course) and configuring the player on the subsonic server running on my windows 10 machine to be limited to 320kbps, the iSub app only plays up to 192kbps.

Any suggestions?