Reclaimable Space

So I have a ton of ‘reclaimable space’ and it is growing. What do I do with that? What does it mean? I can’t find anything in the docs anywhere.

OK, well for those who google this in the future. I found a setting ‘prune sector roots’ under ‘advanced’ which looks like it is at least supposed to be on by default but it was off for me. Perhaps I accidentally turned it off. In any event my reclaimable space is now decreasing.