Hey Ibol, thanks for the prompt reply! I posted my comment before I went to sleep last night, and you responded before I got up this morning. You must be a real 24-hour-a-day guy!
More importantly, I appreciate the gist of your reply. I am glad to hear that my issue was at least - arguably - a type of bug. I was dismayed by the thought that this transaction might have been intentional. In fact, now I feel pretty good about this! Apparently I tested this game, in a sufficiently strenuous manner, that I actually discovered a bug ...
Wow. I have never had that experience before ...
...
BTW, one may wonder why I had diligently "Paid Forward" such a large amount of credits. The thing is (and this is not a complaint) I had found this game sufficiently challenging, even on Easy, that I really did not know how LARGE a stock of credits might be useful, if I started my next game on the Medium or Hard levels. This perspective probably also reflects my very limited experience with "rogue-like" games ...
Anyways, no major harm done. I still have some 18 million credits left; and I will just make sure to pay forward a large chunk of them, before I resume my adventures. As long as I know what to expect (the inherent limitation) I can work with what I've got. (I do think you should put a known/identified limit on "Pay it Forward" donations, perhaps in the next update.)
So: "All's well, that ends well".
Thanks again!