Set a start for cumulative data



I have a calculated member as follows:
[Measures].[Issues closed])
When I use this, the Cumulative data starts accumulating at the dawn of time. I would like to report this on a specific period, but I can not figure out the correct filter to only use data for the last 3 months. In other words, I i filter Time to only show the last 3 months, the value starts at 6000 in the first period shown when I want to start at 0.

I am not sure if I need to do something on the measure or if I can create a custom time member to only get data for the last three months.