Count the number of customers base on the filter

Hi community,

i've created a filter to filter customers base on their total sales.

basically 3 buckets

<$50

between 50 and 500

more than $500

how do i count the number of customers thats showing in the view and reflect it in the title of the workbook ?

i tried using

{Fixed [Sales Filter] : Countd [Customer Name]}

which doesnt work as it says sales filter is a measure not a dimension?

any help would be appreciated.