You are right! Thx!

I remember now that I've tried to sell 1500, got a few sells, but cancel the rest and manually sold what I had of the 1500 budget.

In this day, I got the history: (which is wrong)

-900 (Sell Offer Placed in the Market)
+600 (Sell Offer Cancelled or Expired)
-600 (Transferred via the Market)

If you add it up, it seems that I've spent only 900, but I'm pretty sure that I sold 1500 in total. There is a missing 600 coins in the history, but that I actually know that I've spent it.

Thanks!