Difference in 265cc and 280cc Natrelle Inspira low plus?

It is unlikely that you will notice the difference in the width of the 280 or 265. Since you are going down 2 cm in projection, it may be wise to go down a bit in width, or you may feel that you have a flat wide breast. You mention your width is 12.8, however the thickness of your breast tissue also plays a role in choosing the implant

I recommend that you follow up with your surgeon's office for sizing visit to confirm your size, that way your tissue characteristics and breast shape can also be taken into consideration, rather than only the numbers.

All the best to you,
Dr. Nancy de Kleer

The extra 15cc drop is negligible. It's one tablespoon. Dropping from 415 to either 265 or 280 is a big decrease that may require a lift if you don't want to do it in stages to allow your breasts to contract. The only way to know for sure is to book a consultation with a board certified plastic surgeon near you to see what your options are. Best of luck!