Just a side note that may help. Check https://en.wikipedia.org/wiki/Standard_deviation#Standard_deviation_of_the_mean 

and

http://www.owlnet.rice.edu/~dodds/Files331/noise_notes.pdf . Quote from the second link "Signal averaging exploits the fact that if one makes a measurement many times the signal part will tend to accumulate but the noise will be irregular and tend to cancel itself. More formally, the standard deviation of the mean of N measurements is smaller by a factor of  square root of N than the standard deviation of a single measurement." 

So, maybe they want to accumulate the same signal in these cubes....