HD
Pctl is Percentile. The 10th Percentile is how long the 10th quickest out of 100 flights takes, the median the 50th & the 90th Percentile how long the 10th slowest takes. Standard deviation is a measure of whether all flights take the same time to taxi or some take much longer than others. I have had a taxi time of less than 5 minutes at Miami & over an hour at JFK.
No surprise that JFK is at the top of the list both outbound (32 minutes) & inbound (16 minutes).
Another source giving detail by airline, route and month is the US Board of Transport Statistics T-100 reports for international services
RITA | BTS | Transtats
You will see in Field Name that you can select Ramp Time and Air Time, the difference being combined taxi in & out times. (Generally its only available for US not foreign carriers.)
Its all a bit complicated but I have done some work on the seasonal variation of block & flight times for Atlantic routes & if you send me a private message I can extract the information from this.
BTS also publishes domestic taxi in & out times but I've not got around to doing any work with those statistics.
RITA | BTS | Transtats