Can someone explain to me about the Score Report? Specifically what the "Assessment Score" and "Approximate 3 Digit Score" is supposed to indicate?

I want to use the "http://clinicalreview.com/ClinicalReview/resources/usmle-score-calculator.html" calculator but don't which numbers to use for the calculator.

Is the UWorld Assessment Score or the UWorld Approximate 3 Digit Score supposed to be entered in the "UWorld 3 Digit Score" portion of the calculator?

Also, is the USMLE SimTest four tests percent that I got correct supposed to be used for the "UWorld QBank Percent" portion of the calculator?

Thanks for any help. My brain is frazzled after doing these tests and just trying top figure out if I'm doing good and ready for the real Step 1 Exam.