Thinking it wouldn't hurt if she made a wish before Jon got back, Karyn decided to make the one wish she had been planning on making all morning.
"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 and Karyn was relieved when she felt her too-large breasts shrink to a more manageable size. But then her relief vanished as something else began to happen ...