I am not sure why you are counting the records multiple time, however in order to achieve the desired result you may need to tweak the data a little as you have to show all the months and the created on doesn't have all the months or for that matter the expire date.
In order to achieve the results you have described in your requestion you may need to change the data in below format this can be easily achieved using custom SQL or Union.
id name Date Event 1 a 1/1/2015 Created 2 b 2/1/2015 Created 3 c 1/10/2015 Created 4 d 1/20/2015 Created 1 a 3/2/2015 Expired 2 b 2/20/2015 Expired 3 c 2/1/2015 Expired 4 d 2/15/2015 Expired
Below is the results , Let me know if this works for you?
Differences between the CROSS JOIN and UNION method are described in Re: Headcount, when given the Arrival & Departure Dates. Various material about this is collected in FAQ: Open & Close Dates.
The attached uses the method described in CROSS JOIN with Tableau's join dialog
but with your demo data plus an extra field for amount:
Attached Workbook Version: 9.0