The analog audio inputs on the CLSO-840 correspond to the HDMI/HDBaseT outputs:
Audio in 1 is tied to HDMI Output 1
Audio in 2 is tied to HDMI Output 2
Audio in 3 is tied to HDBaseT Output 3
Audio in 4 is tied to HDBaseT Output 4
For more info on audio routing on the CLSO-840, please see this video
Article ID: KB01008