What does channel num_updates mean?
For some reason stackoverflow has a 50 reputation limit on comments, so I must use the answer box to point out that Karlo's answer is not correct - or at least does not tell the whole story. I understand that this is not the correct use for the answer box, blame stackoverflow's poorly thought out reputation limits.

I have a node with a few (outgoing) channels, have not spent a single satoshi with it yet. So the "remote balance" of the channels has always been 0, in other words there have been no balance updates. Yet the number of updates in the channels is non-zero.