I'm not sure if this is quite what you are looking for, but my interpretation of your requirement is that you want to see a line chart that shows every point for the current parameter setting and every lower setting (which does not form a straight line as shown in your mockup, so I'm not sure if I interpreted that correctly).
After putting together the solution, I wasn't even sure if the parameter was needed, so I didn't include it in the first sheet. There's a second sheet that shows how the parameter could be incorporated to filter the results.
Here's what I did:
1. Create a Bin called [Days bin], with size 1, from the [Days] value.
2. Put [Days bin] on the Columns shelf.
3. Put CNT(Id) on the Rows shelf. (I used CNT and not CNTD because I didn't see evidence that CNTD was needed for this data.) Configure it as a Running Total over "Table (across)".
For the parameter version, I created another calculated field:
And then replace CNT(Id) with the calculated field. (I also adjusted the formatting so that nulls are "Hide (break line)" to avoid warnings in the corner of the display.)
Workbook attached (version 10.1.4).
Thanks Jamieson! This is exactly what I'm looking for. The line in my screenshot was more of a mock illustration if the distribution was even across the days.