Change how big each cup size is that way.

She again converted to, and back from centimeters, and saved her changes. Her breasts are still a B cup, according to her bra, but judging by their size, before they would have been at least a D cup, maybe more. She checked a photo on her phone of Sara, and was a little relieved, and a little disappointed to see that while they're huge, they're not so big as to be impossible, although she would have guessed they were caused by implants if she didn't know better. She noticed something a little odd, and looked at the rules. It turned out that sag was calibrated based on cup size, so her larger breasts were no less perky than when they were small.

She looked at Sara's new breasts. They still looked pretty good, and Anna was about as big as Sara was before... Then again, Sara might look pretty weird with... she tried to do the math, and quickly saw that Sara would be far beyond original cup sizes.