Audio Interface inputs

Audio Interface inputs

So this is a bit of a noob question… NI’s interfaces are as advertised and even give more than that. IE - Audio 8 actually has 9 inputs. I’ve been looking at the saffire pro 24 for my home studio. It says it has 16 inputs, but I only count about 6. I’ve seen this type of discrepancy on a few other interfaces as well, so what am I missing here? how am I supposed to get 16 inputs into this interface when there’s obviously a lot less physical inputs on it?

The numbering in I/O is confusing.

Ch 1-2 are the xrl-combo jacks on the front.
Ch 3-4 are the line inputs on the back.
Ch 5-14 are the “Optical In” on the back - it supports an 8 channel ADAT connection.

Ch 15-16 are ??? Maybe the MIDI in, or the SPDIF in…I really can’t tell.