(imported comment written by BenKus)
I am impressed that you have gotten so far. The stastical inspectors were created by one of our lead architects a little while back and she has a PhD in Math from Berkeley and it seems like you need to have quite a background in statistics to figure out the statistical inspectors (for instance, we have an inspector "logarithm kurtosis of "… want to know more about kurtosis? See here: http://en.wikipedia.org/wiki/Kurtosis)
To answer your question (or at least try):
The goal of the statistical inspectors is to provide historical information on a property, but not require an ever-expanding amount of storage. For instance, in your example you are storing the amount of Fixlets relevant every 6 hours for all computers. Rather than keep every value for every computer over time (which would grow and grow and get computationally more expensive to process as it grows), we “aggregate” the data in “statistical bins” that let you get the data you are looking for (like the total, mean, max/min bound, standard deviation, kurtosis, etc.).
One of the ideas in the statistics is that you can consolidate the statistical bins over time to save space/computation. So you may care about the values every 6-hours for the last week, but you don’t really care about the values 1-year ago on a 6-hour interval. So the system will compact the data to let you get the data on a 24-hour basis over the last year.
So my guess is that the data was aggregated to 24-hour intervals, which is why you can see the info if you use the multiples of 24 but not 6.
I will double-check with a developer to make sure I am giving you the proper info and let you know if I find anything new.
Does that help?