SYMAX addressing assistance needed

[sweible]

Hello all and thanks in advance for any help on this. I am working with a symax 400 processor and i'm trying to wrap my head around the addressing. I think I have a basic understanding, but still need a little help. I put my thought inside "" "". I hope this isn't too confusing.

From the Rack addressing screen

01 ---- |---- |------ ""400 Processor""
02 0001|0128|LI ""Comms, Passing Registers 0001-0128 to remotes""
03 0129|0144|IN C1 ""Digital Input card, "C1"??"
04 0145|0164|OUT 84 ""Digital Output Card, "84"??""

"Next Page"

LI Slot 2 Channel:1 Drop:1 ""1st remote Rack""
01 0001|0008|I/O ""Comms, 8 Slot Rack??""
02 0009|0024|INT 14 ""Analog card, 14 not sure if Input or Output??""

"Next Page"

LI Slot 2 Channel:1 Drop:2 ""2nd remote Rack""
01 0025|0032|I/O ""Comms, 8 slot Rack??""
02 0033|0072|IN C1 ""Digital Input card, "C1"??"

"Next Page"

LI Slot 2 Channel:1 Drop:3 ""3rd remote Rack""
01 0073|0076|I/O ""Comms, 4 slot rack??""
02 0077|0084|Out 84 ""Digital Output Card, "84"??""
03 0085|0092|Out 84 ""Digital Output Card, "84"??""
04 0095|0124|Int 14 ""Analog card, 14 not sure if Input or Output??""

"Next Page"

LI Slot 2 Channel:1 Drop:4 ""4th remote Rack""
01 0125|0128|I/O ""Comms, 4 rack??""

Last couple questions, for now anyways.
In the ladder, I see addresses marked with I, O, R, and N (example I0348/16), however i don't see the 0348 register assigned to the addressing listed above. Why is that?
Is if safe to assume that the "I" is a physical inputs on a card, the "O" is a physical Output on a card, the "R" is a internal.

Thanks again for any help you can provide.