I noticed this issue frequently in the past month, and happened with me personally at least three times. Some sell orders for some reason after being sold and processed are left with so zero balance instead of disappearing. The reason these sell orders didn't disappear because there still some fractions of the sold order wasn't processed. I had this issue myself, I clicked one of the orders, and bought all of it, then, I noticed the same order didn't disappear, but rather became zero, and there is a fraction of the price wasn't processed. In order to clear the order, another sale order has to occur, and fees of 0.5 Ardor has to be paid to buy basically 0.00001 Ardor or Bitswift.
Here is an example of this issue in Ardor->Bitswift exchange: https://i.imgur.com/SLiFdZr.png
I hope this issue getting fixed soon.
Requested Feature: Since the post is about buying and selling, I would suggest "buy max" or "sell max" feature, which is basically allowing buyers or seller to use the maximum that they can buy or sell of their balance – excluding fees – instead of them counting that manually.
submitted by /u/abokhalel2
Source: Ardor News
Fractions are not processed in the Sale orders in Ardor Client