LogFAQs > #977238538

I've heard terms like "99.5th" percentile to describe the top 0.5%, so I'd suggest that there are actually infinite percentiles.

In the context of that Oxford definition, though, just think of "in the 90th percentile" as being in a group that comprises 1% of the sample population, ranked 90th if ordered from lowest to highest. Colloquially, people tend to interpret that by counting from the top instead of the bottom (though it's often as "you're in the top 10%" and not "you fall into the 10th percentile from the top," which is vaguer than perhaps it ought to be, but no less accurate than somebody saying "I'm in the top 10" when they rank 10th), but that's just a matter of frame of reference, not a failure to understand the concept.