It's a little hard to figure, because not all challenges are created equal. For example, my absolute highest numerical finish is 13th with this shot: , but that was in a "specialty" challenge with only 22 entries.
Of "legitimate" challenges, this one is the highest rank numerically with a 16th place out of 60, for 75th percentile, while this finished in the 90th percentile, though it was 22nd out of 202 entries.
So my highest averaging photo scored the worst in placement and percentile. My best placement was 36th, which is the lowest scoring of the three examples. My highest percentile has an average and a placement somewhere between the other two. People get worked up over score and place, but really the meaningful statistic for competition is the percentile - 43rd place means a hell of a lot more out of 449 than it does out of 177. ;)
I've yet to break a 6.0, and my highest finish so far was 50th. Of course, i was thrilled with that. I can see my shots improving by leaps and bounds, but i'm not good at choosing the *popular* shots, and my PP skills need quite a bit of improvement.