Originally Posted by MumOfThree
I think the difference between 99th and 99.9th is quite hard for a lot of people to comprehend without it clearly stated. Although the numbers mean the same thing 1/1000 v. 1/100 sounds much more different than the percentiles.

Its more than that. There is a comprehension vs time spent component. A 99.99 child just needs a few minutes to get something vs hours for a kid at 99.0 and days for a kid at 95.0.