Karyn looked over her shoulder, to make sure Jon was still in the bathroom, then darted into the bedroom and snatched up the stone.
"I wish I had C-cup breasts," she said. This way, it wouldn't contradict her previous wish of having bigger breasts, because she originally had B-cups and C-cups were bigger. She was just being more specific, which was allowed.
The stone glowed, but nothing seemed to happen. What she hadn't realized yet was that the stone she was holding was actually The Selfless Stone, and her wish was granted to everyone else within range of the stone. That meant that everyone in town except for her had C-cup breasts, whether they were female or not. And since none of them heard Karyn's wish, they all thought it was normal.