Why does analog heat say 4 in 4 out

[Schnork]

Explained here:

Just want to listen music and play with fx of Analog Heat

The Heat is a 4in 4out interface. This means that you can use the clean channel when you want to use it as your computers inter face while still processing another signal thru the circuitry separately. Have a look in the manual on audio routing and how you select what should be audible where and how to set it up. There are a few options and you should be able to do what you looking for.