Inputs - Basics

I’ve been using emonPi, emonTx and emonTh for a couple of years now and am doing a bit of cleanup of my 36 feeds as clearly not all are needed, I’m down to 24 and have a few questions. My emonPi is on the May 2016 build; it’s working & I know if I try to upgrade I’ll break it!

I’ve had a fairly decent look through the online documentation and I can’t see some really basic stuff; specifically I want to know what the data is corresponding to keys in the input for a node.
emonPi, node 5; what data is on key 11? (Current value 64)
emonTh, node 23/24, what data is on keys 5 (values 1 or 2) & 6 (currently negative values around -70 to -87)?

I have nodes 5, 10, 23 & 24 which I know are my emonPi, emonTx and 2x emonTh.

I also have these nodes; 0, 2, 4, 13, 16 & 20. What are they and might I be interested in creating a feed off them?