I am a little confused by your calculation - I would think it would be of the form DATEDIFF('month',#2017-01-01#, [Date in your record])
Where the date is like an order date or some other date associated with the specific record you are looking at
Can you share your workbook?
Let me know if this helps
If we can see your data, we can probably help you out here. If it's confidential, you can mock up some data and replicate the error.
Thanks for the replies, I was actually helping out my superior with this issue and did not realize that he was summing the calculation and the table we were looking at was not drilled down to the smallest level of detail. So multiple rows had the same value for the field in the rows shelf, so those were grouped together when displaying this field. Thanks for your replies, I should've thought of this first.