Don't boot a Kindle while plugged to something, it confuses volumd.
If this still happens without anything plugged, you might have tweaked something else in the config (USE_VOLUMD), which is also a very bad idea on a K4. [Incidentally, if you don't know what you're doing, err don't, but, barring that, use the KUAL extension, it at least prevents you from shooting your own foot with some settings combinations...].
Also, read the docs, because if you were trying to enable USBnetwork, and then are wondering why you see a Linux Ethernet gadget network interface, then you obviously missed the point
.