How do graph/map legends work for numeric and date/time attributes in CODAP?

If you have a numeric attribute or a date/time attribute and color points on a graph or color points or boundaries on a map by that attribute's values, CODAP divides the data into five quintile bins, with each bin holding 1/5th of the cases and corresponding to one of the five colored bands on the graph or map's legend. The leftmost color band/bin on the legend represents the first quintile (the 1/5th of cases with the lowest values, or the earliest date range), ascending to the right until reaching the fifth quintile (the 1/5th of cases with the highest values, or the most recent date range). The numeric or date ranges for each quintile bin/color band are inclusive (not exclusive), so a data point or map boundary can belong to two quintiles if its value falls exactly on the dividing line between the two quintiles (note, though, that CODAP will color the point with just one color, but if you click on either of the adjacent quintile color bands in the legend to select the corresponding points, you will see the point/boundary highlighted for both quintiles). It is also possible for one specific numeric or date/time value to be in more than two quintiles/color bands on the legend. For example, in a dataset where the vast majority of values for an attribute are 0, the first four quintiles may all represent a "range" of 0 to 0.