I'm not sure if it is a bug, but it is worth further investigation. Your post is making me wonder a bit, too...
I decide what to put in my trade binder (or in my bulk trade boxes) based on my inventory numbers. For any recent set (M12 and on), I list items for trade if I have five or more of that card. Recently, after trading things away from my binder (items that my inventory once indicated were in excess of four in quantity), I've gone into Deckbox to adjust my inventory (e.g., reducing the total owned from five to four and the number in my tradelist from one to zero). When doing so, however, I've found many cards that show inventory counts less than four (the minimum number I keep), but when I've gone back to my physical inventory, I find complete play sets (4x of each).
Because I've not been as active on the site over the past six months, I thought I had just messed up my inventory. I've been going through and verifying quantities. Some of the cards that had wrong inventory numbers are ones that had correct amounts a few months ago (because I had exported my inventory at different times). Now with your post, I'm wondering if something is going on...
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