Each card in the I/O tree is given a name. From that name each I/O point is the name with the I/O extension, example(name.0). Individual tagnames can alias each I/O point name. If the tag is for a direct I/O point there will also be an alias listed for that point. If you sort by alias you will see if there are any additional I/O points available, or not used because they will not be listed.
An Output Card has a
C for card Configuration and Status
O for the Outputs
I for Simulating Outputs - I have not played with these at all, so I am not positive of this.
An Input Card only has
C for card Configuration and Status
I for Inputs
Some cards, like a DNB (DeviceNet Scanner), will also have a S for Status.