New Auction API: auction IDs staying, quantities changing?

I’m seeing commodity auctions with the same auction ID change between subsequent hourly data updates. Sometimes the quantities go up, sometimes they go down. I thought an auction, once posted, remains until bought out or expired? With the any-amount purchases of commodities I assumed it’d be possible for just parts of an auction to be bought out, sure, but how are auctions INCREASING in quantity without somehow resetting the time_left field?

Did you find any information regarding this?

Negative. No information anywhere.

I don’t know for sure, but if I understand it right, maybe it is possible, when an existing player already have a trade order for this item, and add more quantity to it?

Like instead of creating another order, it’s just updated the old one, like

Existing:
T-1 | AlexZeDim | Zin'anthid | x1000 | id1| @5g
Have been added
T-0 | AlexZeDim | Zin'anthid | x3452 | ??? | @5g
Result:
T+1 | AlexZeDim | Zin'anthid | x4452 | id1| @5g