Repeated Unique Values on calculated number/category column


I'm using the DateDiff function to insert a new column with the calculated difference in months between two columns that contain Date data.

New Column = DateDiff('mm',[date field start],[date field end])

The issue comes when trying to color (or anything categorical) a graph with this new column, because it has multiple "unique" instances of the same results. For example, there are over 3 "unique values" of "1". This results in a column with 331 unique values, thus coloring my graph in 331 ways, when in reality its got only 58 unique values for my particular data.

I'm attaching a screenshot of the problem.

Hope you can help me sort this out!

(1) Answer