Matrix - Creating Cumulative Sums Across the Columns

Hi there,

I am trying to get a matrix that looks at the cumulative number of orders depending on when a customer made their first order.

The column headers are the order dates, the rows are the date the customer placed their first order:

In this example, 100 customers made their first order in 2018 - in 2019, these customers placed an additional 20 orders, taking their cumulative total to 120.

So far, I have used the matrix visualization to get the number of orders placed as such:

How can I take this data and create the top matrix?

I have tried using the running total quick measure, summing the number of orders across order date (column header) but this just recreated the bottom matrix when I used this measure.

Any help is greatly appreciated!