It depends on the sim they’re asking you to do. In case of FAR, I found that the actual sims (1-2maybe) seemed to be split into two parts at times. One part is noticeably harder than the other and will not relate to the second part. So if you messed up first half of the sim, the second half will be good opportunity to get partial credit for the sim as they’re likely to be a lot more straightforward.

Then addressing your second paragraph, unfortunately no one knows how they grade sims if they give partial credit for correct application but incorrect numbers used. If you used the correct entries, I do like to believe you’ll get partial credit because it requires studying to know the correct entries. But again, no one really knows the mystery In how the sims are graded.