Default I/O settings different each time (with same hardware)?

I have an Apogee Symphony I/O and I'm running PT11 (vanilla). When I create a new session I usually go into PT I/O... and click the "Default" button on the inputs, outputs and busses.



What I find confusing is that sometimes the inputs default to:



In 1-2

In 3-4

In 5-6

etc..



And other times (for no reason it I can tell) it'll say:



In 1-2

A Mic 3-4

In 5-6



Where is it getting these default names from? Even if I don't touch anything in Maestro, Pro Tools might give different default input names, apparently depending on the wind.



It's easy enough to manually rename them, but I want to understand what's happening.



Thanks,