In Sonar selecting the input from the 18i20 there's 8 inputs total (duh)... The question is, why does it have the inputs listed like this

 
Instead listing them as 1, 2, 3, etc... ? 4 stereo groups?

That's the way Sonar does it.  I had a Focusrite Saffire Pro 40 and it listed it that way.  I have a Roland Studio-Capture (12 analog mic channels) and it lists it the same way.
 
There have been other threads on this forum about this and how Sonar identifies them. 

You can give the User-friendly names and choose which ports should be shown. Like this:
 

 

Thanks, guys... Just seemed odd that they are listed like that.

As apposed to what?

I am pretty sure that SONAR is simply parroting what the driver is telling it. All of those options are available, and you can rename them if desired to look nicer. I do not use ADAT or S/PDIF, so have them disabled in audio preferences in SONAR. In the old days this helped to streamline performance so SONAR did not have to deal with a potential input coming "online." I am not sure if this is still true or not though, and if the machine can handle it is not a real issue (it just makes the input list cleaner).

^yes - sonar only reports what Windows tells it.  that's why "friendly names" in Sonar are available.