Can I Expect a Good Result with Just 300cc Removed from Upper Abs?

While 300cc's may not seem like a lot of fat, but in someone who is "athletic and toned" as you describe yourself, it can be significant. This is essentially the size of a small grapefruit. Liposuction is best as a contouring procedure, not a weight loss procedure, so losing that "grapefruit" from you upper abdomen can make a real difference. As always, photographs would be helpful, but don't get too caught up in the number of cc's.

You may not have seen more fat in the container after liposuction because you are fit.  For one half an abdomen, 300ccs can make a considerable improvement.  It's not how much is removed, it's how the abdomen looks after the sculpting that counts.

The goal of liposuction is contour, or, it is not what you take but what you leave that gives a great result. The endpoint is judged by skin pinch, contour, and correct feathering. If 300cc will get the job done, then the volume is just right, more perhaps dents and regrets.
Best of luck,
peterejohnsonmd