You could use a Running Total card to automatically build the cumulative totals for you. You could also create a beast mode called DisplayDate (or whatever makes sense to you) that just has a AddDate function in it that would display the next months name instead of the month it is in. This function would do it

ADDDATE(`Date Entrolled`, interval 1 month)

If you don't want to use a Running Total card, you would need to use the Rank & Window Functions in Magic ETL to build the cumulative total.

@GrantSmith wrote:

If you have window functions enabled in your instance you could do this via a windowed function in a Beast Mode instead of a running total card:

SUM(SUM(1)) OVER (ORDER BY `Date`)

And then utilize @MarkSnodgrass 's solution about adding a month to the date for display purposes via another beast mode.

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If you want to count by month then just alter @GrantSmith  SQL:

SUM(SUM(1)) OVER (GROUP BY date_format(`DATE`, '%Y%m') ORDER BY `Date`)

In order for it to work, you'll need to have year-month on the axis.  

This technique we're introducing is called 'Window Functions' check out the video below for more information!

https://www.youtube.com/watch?v=cnc6gMKZ9R8&t=316s

@user025461 , contact your Domo CSM or sales representative and ask them to enable the feautre: "window functions in beast mode"