It depends on your display, graphics card, and your screen resolution.
Looks like you’re using a HT-R393 AV receiver. What display is connected to that?
The -C suffix might mean you’re using an Nvidia graphics card - which one? (where C might be the 4th possible audio device on the graphics card (possibilities are 0, 4, 8, C) which might possibly be assigned to any one of five displays, only four of which can be used at a time, although I don’t know if AMD or Intel graphics don’t have a similar behavior).
The dp-hdmi adapter “supports pass-through of LPCM/HBR audio up to 8-channels and 192kHz sample rate.”
The AVR HDMI inputs supports “DTS-HD Master Audio, DTS-HD High Resolution Audio, Dolby TrueHD, Dolby Digital Plus, DSD, Multichannel PCM”.
Maybe someone here can tell us if that means there is or is not overlap between those two sets of supported audio formats (I think HBR Audio includes stuff like Dolby TrueHD; I’m not sure if Multichannel PCM is the same as LPCM). It looks like the graphics card’s audio driver can use all the formats (what’s listed after Dolby Digital?), so you need to just figure out why it says only 2 channels, 16 bit, 48 kHz. I don’t have a multi channel device to test this myself. I have 3 displays that all say max channels 2 (General tab says “L R HDMI Digital Jack”). Each display has a different number of supported Bit Depths and Sample Rates. The HDMI displays show more options (even if connected to a DisplayPort port using a passive DisplayPort to HDMI adapter). The DisplayPort display shows one Bit Depth and one Sample Rate like yours. None of mine support any compressed formats (Encoded Formats).
Some audio formats might not be compatible with 4K@60Hz 4:4:4 RGB video (I’m not sure about that). It depends on how much bandwidth is left over for the audio.
Don’t the Encoded Formats allow more than 2 channels anyway?