In my experience NS wasn’t that deflated in comparison to Kaplan. So I would take that 511 as a ~511 on the real thing. In a few months it’s hard to predict the progress, it depends on your study skills. I would say you have a good chance though.
I got 507, 509, and 511 on the 3 NS tests I took and then ended up with a 521 on the real test. I think NS is more convoluted than the AAMC stuff, so it looks like you’re on good track 🙂
I’ve read a lot of people’s experiences and it seems that NS is inflated under about 507 and then deflated for scores above that. So, you’ll probably be ok. Keep studying hard!
My hunch is that NS loses much of its predictive value beyond a 508. A 510 average could mean a 509 or a 521. The exams are more of a time crunch than the AAMC's and the questions are oftentimes more strangely phrased, so this wouldn't surprise me.
Focus on evaluating your content knowledge and problem solving skills over fixating on the score.