Numbers in the Kanban module

I couldn’t find any information on why there are numbers in the Kanban module. I noticed Kan.ban doesn’t have any numbers (or at least they’re not visible).

I also noticed that it is sharing the same number pool as the Issues module. I guess in the grand scheme of things it doesn’t matter that the numbers are non-sequential, but I was quite confused until I figured out what was going on.

I’m looking for a clear explanation to this.

Thank you