The implant volume is what it is. Because one often tries them on by putting them in a bra, they tend to look slighlty larger this way. How much is hard to predict.
None are lost, just a little different form typically and a little longer to reach final projection behind. Twenty-five ccs is only a shot or two of Tequila, almost imperceptible in that range. Breast augmentation is a dimensional operation, not a volume operation. Obviously you end up with a "volume", but it is how it is dimensionally distributed that determines your result.