PowerBI matrix visual show frequency

Hi,

I am trying to make a PBI matrix that looks like the screenshot below - with frequency indicating how many entries there are for the particular staff id.

I am able to put staff_id and description as 'rows' , and amount as 'values' for the matrix, but I am truggling to get the frequency showing in the second column. What I have so far are something looks like below:

Thanks a lot!