How to get count without showing customer_id

[newyork66]

I have a customer_id field. I want it to be counted, ( group by YEAR and MONTH), but I dont want it to be showed. Do you know how I only get total count number for YEAR and MONTH without showing each Customer_ID?

[rockytopmark]

Have list with 3 columns, [Year], [Month] and [Customer Count]

Customer Count expression is: count([Customer_ID])

Group the list by Year and Month