This statistics is similar to Number Differences Sum statistics except that it divides all the possible sum values into several ranges.
The values are divided into chunks of ten (1-10, 11-20, 21-30, etc), chunks of 30 (1-30, 31-60, 61-90, etc) and chunks of 50 (1-50, 51-100, 101-150, etc).
See also Number Differences Sum filter and Number Differences Sum statistics.