Also I don't know if it's a bug or not, but I only saw the 7 icons once ever, won with them, then never saw a 7 ever again. I think they might've just gotten pushed off the reels by the purchases in the shop outweighing them.
Some icons disappear after you complete them, because they don't have any effect anymore. 7's will be extended later, but since this game is a PoC, it may be only in the bigger game, which will contain this minigame.
