It's more like a glitch, not a bug.
During the burn process, if I have chosen to burn several copies of the same iso, the program indicates that I am currently burning the "Copy: x of y". So far so good.
But, if I change my mind and want to make more (or less) copies of the particular iso image, I go to View -> Queue, select the iso file, check the Set copies checkbox and then set the new number of copies.
However, this change isn't reflected to the "Copy: x of y" label, until the current write operation is completed.
This caused me a confusion, until I re-opened the Queue window and saw that the new value is still there.