Sometimes you'll see Duplicate FBM Import in your Inventory History.
What this means is that Listing Mirror found and imported a duplicate listing in your listing source channel. Because the channel we imported it from was the listing source, if the QTY doesn't match between the channel and Listing Mirror, we will take the channel's QTY and use that amount instead.
In the screenshot above you can see an API Update in November that puts our MF QTY at 2. Two months later, in Feb, we found and imported a duplicate listing. The channel it came from was the listing source and it had 48 QTY which is different than the 2 we previously had. So we take that QTY and use it from there on out, unless you have a duplicate FBM strategy to decide otherwise.