The two-digit score on the USMLE score report is NOT a %-ile rank. In fact, the NBME stopped reporting %-ile rank scores with the class of 2003's admin of Step 1.
The two-digit score that is reported is directly derived from the 3-digit score. To pass, your 3-digit must equal or exceed 182 and the 2-digit equivalent is 75...it has to with the language w/i several state and residency programs regarding passing scores on the medical liscensing exams.
So, if your friends actually got a 99 on the 2-digit score, while excellent...it really is not a %-ile ranking score.
Now the COMLEX reports your raw score, pass/fail & a %-ile rank.