Meaning of "change" attribute in API response?

I'm building something that uses the Danbooru API, and when I was looking at the response from the post listing, I noticed this attribute called "change". What does it refer to?

I noticed that it decreases the further back in the past the image was uploaded, but I couldn't figure out what it's for.

Can anyone help?

Last tag edit, hence order:change_desc.

It's a global counter incremented everytime the image metadata (tags, rating, source, etc.) changes, so searching for "change:>n" allows you to find all edits since the last sync.

IQDB uses it to get updated ratings to allow searching for only safe image results, for example.